There were different styles of pilots used for the ANH-built heroes, including the Red 3 open-faced one. The ANH modelers also used different combinations of arms from different kits for the hero pilots.
It doesn't "tend to indicate" that at all, IMO. That Red 3 hero was built for ANH, using an ANH-era hero armature and ANH-era hero castings, and finished in a most ANH-era style, especially when compared to some of the paint jobs on the "nice" pyro models.
Those pictures of the Red 3 hero miniature in the "Art of Star Wars" book were taken during production of the first movie. I know because I have more of that same set that have never been published. They were taken at the same time as the other photo-studies of Red 1, Red 2 and Red 5.
Of course, you're free to speculate all you want, but if you're going to challenge the origins of the Red 3 hero miniature, be prepared to be asked to provide some kind of actual evidence beyond a simple hunch.
I'm not speculating, I'm trying cut through all the speculation and look at the physical evidence from that period. The Rosetta Stone is the picture of models lined up on the table. It is the evidence that clearly shows all of those models existed at the same time during ANH. So we know for a fact from those pics that Red Leader hero, Red Leader pyro, Red 5, Red 4, Red 3 pyro, Red 6, Red 12, Tie Killer, MOM-Y, and triangles-Y are all contemporaries. There are 4 models missing from that display. We know Blue Leader and Red Jammer were built first and then sent to the UK right away, which is a plausible reason for their absence on the table. The other two absent are Red 3 hero and blue/gray/tiger-sprocket Y-Wing. Although blue/gray does not appear in photos with any of the other models (unless the hypothesis that the Y cockpit on the table is blue/gray is correct), blue/gray is visible in the film during the trench run and visible outside Gold Leader's cockpit (both times alongside TIE Killer). By process of elimination, that leaves Red 3 hero as the only model that does not appear in a photo alongside any of the other models, and I have not so far been able to pick it out in the film itself either (I'll keep looking).
That leaves the only evidence of Red 3 hero's existence during ANH production being the Red 3 hero pics from "Art of Star Wars" and the unpublished pics from that set. They do look similar to the other hero pics of Red 5, Red Leader and Red 2; which is why I first thought they were pictures from ANH period. But now I can't say that they are definitely ANH or ESB, because being similar in appearance does not mean the pics did not come from ESB production. Both are equally valid. Unless the molds were destroyed after ANH, there's no reason an ESB X-Wing couldn't be cast from them or even assembled from left over parts from ANH. So that is not evidence for ANH or ESB, still equally valid.
I have pictures of Red Leader pyro, Red 2, Red 4 and Red 12 with closed face helmets on the pilots. I can't see pilot faces for Red 3 pyro, Red 5, Red 6, or Red leader pyro. Do any of these have pics of them with open face helmets similar to Red 3 hero?
There are only two sets of hero and pyro models to compare, since Red 5 hero and Blue Leader/Red 2 hero did not have pyros. So the only thing we can say is that they matched up the Red Leader paint jobs pretty closely, and they did not attempt to match the Red 3 paint jobs at all. There's no real rule that can be derived from just those two examples.
There are postings referring to a "Blue 3 Biggs" pic similar to the "Blue 4 John D" and "Blue 12" pics. But the original posts of these pics are now broken links. Was this the pyro or the hero?
Unfortunately, the Famous Spaceships article X-Wing count doesn't match up to the know photos of ships. They don't use the terms pyro or hero. The article refers to three types of X-Wings being made for ANH. It mentions 5 "stage models" with lights in the engines, cockpits and weapons tips being made. But 3 or these "stage models" had "motorized wings" and 2 did not. And then there were 9 models "made from silicone rubber molds and back-cut for use in scenes in which they had to explode". If the 3 with "motorized wings" are heros, and the 9 that "had to explode" are pyros, then what are the other 2 "stage models"? Since there are 4 heros with "motorized wings" (Red Leader, 2, 3 and 5), and 5 pyros (Red Leader, 3, 4, 6 and 12), it doesn't match up well to the Famous Spaceships article. Do all the hero ships have "motorized wings", or are some non-motorized? If "stage model" and hero are the same, where is the 5th "stage model"? (The rumored stolen model?) If all 5 pyros represent the ships that "had to explode" and not "stage models", the other 4 of the 9 might have been the slipshod pyros that we have a few pics of. I don't know how to make the photographic evidence fit the Famous Spaceships count otherwise.
Extraordinary claims require extraordinary evidence. But which is the extraordinary claim? That Red 3 hero was built and used for ANH, even though it has a different pilot from the others and it does not have photo evidence of it around the other models. Or that Red 3 hero was built for ESB, even though it uses the same hero molds as the ANH models and paint technique while being photographed similarly to the other models. I'm on the fence unless I see some evidence that clearly links it to ANH.