but i'd bet all of their Iron Man suits are really accurate down to small details....Alien, Predator, Terminator obviously aren't their main 'let's do this line right' franchises....
I think both your and A-Dev's statements are true tho, aren't they - so it's about the reference they've got. For all the "current" stuff, they've got scans of actors as part of their contracts, they've got availability of actual suit model data for things like Iron Man, etc etc etc. Merchandising is built into many of these shows. But for the old stuff, HT have got Google images, and the pause button on the remote, and then it's just how fussed someone is, and how much time/budget they have.
I'm exaggerating a bit no doubt, but you get my point
Not saying I like it, necessarily. Just I'd say there's a good chance that's how it is.

EDIT - I'm going to pre-empt someone pointing out the current OT Star Wars figures contradict what I'm saying