Just because the name is Iron Spider doesn’t mean the costume is hard metal. It’s a name. Iron Man made it so, Iron Spider.
Even in the comics, it’s some sort of flexible material. And it’s shown ripped and tattered in that famous panel where Punisher is carrying him.
No way Tony would designs a suit for Spider-Man that wouldn’t be flexible material like on the Hot Toys figure. One of Spider-Man’s strengths is his agility.
I’m guessing it’s some sort of flexible nano metal weave in the film. Whatever material they used had to mimic the suit’s properties so I think it’s fine (as long as it holds up). They had to get Marvel’s approval for it.