While Holland likely understands that, he also wants to give the fans what they want, so he starts putting his autograph on a bunch of Spider-Man comic pages, which he apparently just carries around for this purpose, wads them up into balls and starts flinging them out the window to the assembled crowd below.
Tom Holland starts his Instagram video by saying he’s been told he’s not allowed to leave the hotel.
There’s a crowd outside that will almost certainly mob the new Spider-Man if he goes down there.
It’s not uncommon in situations like this for actors to be managed like this.