I was in a bit of a hurry when I wrote my post so I didn't really get all my thoughts out, but you're picking up on something that I was thinking but didn't articulate. His tweet puts a huge burden of expectation on someone who frankly is a stranger and didn't ask for it. That would be a very uncomfortable place to have to navigate as a celebrity with someone you don't know approaching you with something like that.
She either was/is genuinely very cool with it, in which case good for her, or might think she doesn't really have any other way out of it without potentially looking bad or causing some bad PR or news for a reason she doesn't want. Like she should be completely within her rights to decline if she wants, but you know there'd be people writing op-eds with, "Gabrielle Union Refuses Injured Football Player's Wish to Honor His Late Father on Live Television" headlines if she didn't feel comfortable.