Thats not a rumor. Its an opinion.
A rumor is an unsubstantiated fact.
This says “Giannis is unhappy about not being named to all defensive team”. Not “unhappy with Bucks and wants out”.
If Knicks are “rumored to be in talks”, and some basis of why that was uncovered, its a rumor.
Knicks want a star and have assets is not a rumor.
If Giannis is selling his home and shopping in westchester, its a rumor.
If “league sources close to the team are telling that Giannis is going to ask out”, its a rumor.
If Giannis grumpy and tweets about not making a team, and a writer thinks of three teams that would want him, its not.

I’ve seen variations of this “rumor” On URLs like:
Nba-inside-rumor-poopy-butt-after-taco-Tuesday-Facebook-clickbait-I-know-what-is-up-but-this-is-a-BS-rumor-website.yams.potatoes