It’s a lot simpler than that. Giving your product away shouldn’t be a “gotcha”. Nobody gets trolled with a free Netflix subscription.
I can send LeBron Nike snickers. That's not illegal. But if I force those snickers on his feet (whether in person or in Photoshop) and prop him out and take photos of it for my ads, that's false endorsement.
Do these Twitter users have the option to NOT show their fake Blue status? No. Did someone ask them at all if they want it? No. In the case of LeBron, actually Twitter asked LeBron's team and they said "WE DECLINE" and they put it on, anyway!
IT IS FALSE ENDORSEMENT.