"Bullet sharpens what you already know" ++ Exactly do not underestimate what you already know. With a sharp trained mind it prevents blunders to happen.
Is Bullet Chess Good For Improvement?

Bullet is good for honing your quick tactical vision, for playing with the initiative, and for practicing your opening knowledge.
But if you're wanting to be a more precise, accurate player, then bullet is not ideal. It's furious and sloppy chess - especially near the end of the game, when time scrambles happen.
Ironically, the endgame is where you want to play the most precisely of all. But in bullet, this is the phase where accuracy tends to fly out of the window - and both players are simply trying to flag each other by any means necessary ...
So yes, I'd say bullet has some benefits. But it also has some big drawbacks, too.
I think bullet teaches bad habits that a developing player will have to unlearn.
yes, it may be fun. But if you want to become a strong chessplayer, stick to slower time controls until you have mastered the basics.
Different for everyone. One of my friends tilts badly after playing bullet . It personally doesn't affect my chess that much but helping speed and pattern recognition/opening . My other friend solely plays bullet and got to 2200 bullet in 18 months, by the time he played his first rapid, he was 2070 just by playing bullet and studying a tiny bit 🤷♂️. Obviously the latter is rare so it's good but in moderation
He already had good rating in rapid. Anyway, 2200 is very good.