I think that might be a little reductionist... Qui-Gon tells Anakin we all have midi-chlorians, and that they're our connection to the Force. There was stuff in George's notes and conversations with ADF back in '75 when the novel was being written that, basically, had that anyone could learn to wield the Force to
some degree. Higher midi-chlorian count means more of a conduit/more ease/more inherent talent. Even Anakin needed years or training to be able to do more than have the precognitive/instinctive flashes that let him be a good pilot. Why I have such a problem with Broom Boy in TLJ.
But, beyond the dent and physical construction, the helmets are otherwise entirely different, from paint colors used to specific color scheme to weathering to detailing. Hot Toys actually helped me out a lot, here. Their notorious pursuit of accuracy led them to color-match the original props in the LFL Archives, and they recreated all of the topical weathering and markings. This is the best side-by-side comparison under the same light you'll probably ever see:
View attachment 1539528
View attachment 1539529
Regardless of anything else, we're supposed to believe those are the same helmet.
I have a feeling Boba and his apparent age-mates would've been in a lot of the same areas getting the same training at the same time. Probably what helped one young trooper, at least, develop a fixation on his "father" and want what Boba had.
Simple. Two ships. One came and went with Boba --
Slave I -- and the other was the imposter's ship -- unnamed
Firespray.