I never noticed 'em until you pointed that out just now!
I was going to say that they were there for the human fig to perch on his hand, like HA Bumblebee, but, looking at them now, that wouldn't work
It looks like the 'thumb' was originally molded to swivel independently from the rest of the hand... so who knows what 'play positions' Hasbro had in mind during development

- I think integrating the human figs in 'traditional' Human Alliance beyond sitting in the driver's seat are an afterthought, as they never seem to fit anywhere on the damn cars anyway (Barricade/Frenzy being the exception that proved the rule)
I think it may be a clip for Steeljaw's chain, but I can't find Steeljaw at the moment (put him away for safekeeping as I'm diggin' Leadfoot at the mo, he's around somewhere)
I find getting Roadbuster to bot mode fine, it's getting him back to vehicle mode that's the pain - the door panels should be all flush with each other, and always seen to shift around - but the weaponised look actually has panels looking like the cars' bodywork is split into pieces - I have less of a recognisable 'car mode' to work back towards, if you know what I mean.
It's been said countless times before, but I think they should have picked a scale, and went with 'weaponised' and 'stock' modes within that scale - as an Alternators devotee, I would have preferred weaponised looks for all 3 in deluxe, and stock looks for HA.
