Well I mean body shape, to a degree, it appears there is significant variation with potential to success. I'm not sure I'd extend that line of reasoning to like any body shape known to man period has equal chance of success. Also, there seem to be some common characteristics, even if the legs are longer relative to the torso or vice versa, usually tend to be smaller through the hips relative to the shoulders which is mechanically advantageous. There are plenty of females who have wider hips and relatively narrow shoulders and this is generally not a body shape I see much in gymnastics.
But I mean, beyond that, obviously there are other physical characteristics which appear to be much better indicators than body shape, within certain parameters. Certainly the presence of fast twitch muscle fibers, general tendency towards lean muscle would to me be a better indicator than anything shape wise. I've definitely known some larger girls who were very successful at gymnastics, but again shapewise they had an overall body distribution that had certain characteristics. Perhaps we could argue that stuff is the result of years of gymnastics training anyway, so maybe, I don't know. I'd definitely agree it's not the most important trait, simply because there is plenty of variation and other traits account for more. There seems to be less variation to me in rhythmic gymnastics. I have had some friends L10/elite in RG and from what I see I never could have made it (not just not being flexible I simply don't have the body shape that they ALL seem to have to me. Just an observation. Same thing with pre-pro or pro ballet. I don't have the lines). In that sense we tend to see more variation in artistic, I think.