I follow all 5 on twitter, and between tweets and what was said on the show, it seems like, whomever brought up the change, none of the 5 are exactly "happy" with it. It also seems to have been decided/building for a while, but after the start of this season*.
For most recent seasons*, the crew has dropped hints of what they're filming, and then sneak peaks the closer to airing. A lot of times, they'd even livetweet the episodes as they air on the East Coast (incredibly annoying for those of us on a 3 hour delay on the West Coast, tbh). This season*, they started off with that for an episode or two, then suddenly they weren't talking about the episode anymore. The build team was still talking about their stuff (Kari's dress for the Emmy's, for example), and Jamie and Adam were talking about the legs of the tour going on, but not the episodes. Then, this episode airs on the East Coast, and Kari said something along the lines of "well, the cat's out of the bag, we can say this now". That, and the awkwardness of Jamie and Adam in their goodbye segment is what's telling me that none the 5 of them are exactly happy with it.
The show's been having problems a lot lately. I've enjoyed the specials (the Star Wars special was great, and even the Walking Dead one was fun, despite not watching the show), but the rest of the show has been lackluster for me. Discovery's been doing it no favors, either, with every season* having a different time slot, and sometimes they get reruns, and sometimes they don't. For the past few years, they've been consistently scheduling it against something else I watch, that's neither available On Demand or gets reruns, so I've had to choose not to watch Mythbusters and hope they repeat it.
Then, there's the "seasons". There's a reason I've been marking the word with * this whole post. I'm pretty sure that this "season" was the third season this year. I get that shows do split seasons, or a fall season and a spring season, or whatever, but it's just too hard to follow what's going on. I'd see stuff advertising the "season premiere," then, next thing I know, not even 2 or 3 months later, the show's off the air again. I'm not sure if it's a problem with funding or what, that they pretty much air the episodes as soon as they can get them edited, but I'd much rather they wait until they have a decent amount of episodes before airing them. I think this "season" was only 6 or 7 episodes!
Personally, I don't know if I'll continue to watch the show. I've never really cared for Jamie all that much, and Adam is more fun when he's on his own. The build team have always been my favorites, and more fun to watch. Then again, it's not likely that Discovery will air the show at a time when I can watch it, so it's likely to be a moot point as it is.