well i did my first lesson and safe to say, there was things i didnt understand why, however i did not question it either as recommended here because he does know what he is doing.
So.... i dont remember the name of the guy that signed up here not long ago, but he has those 5 free videos for embouchure, airstream, articulation etc. He says most people are taught to lip buzz then explains why not to lip buzz.
So i sat in on my lesson and got told to buzz on mouthpiece, took a bit before i got it to buzz as i wasnt used to it. He also explained why to buzz which also makes sense. Buzzing on mouthpiece creates a very controlled, rich, clear sound. By being able to play all the notes on the mouthpiece ensures good playing for the notes once you plug it into the trumpet. The trumpet is there to amplify what comes out of the mouthpiece. You need to control the trumpet not it controlling you.
I also with my entire embouchure quest here... was told my lips push out. He said exposing all the red part of lip is no good. Said to say DIM. Now keep that shape and use the muscles for support not tighten the skin to play as such. This also helps with the buzz.
His notes are absolutely amazing and clear when he plays so that itself makes sense. However im just trying to cross reference this with this youtube guy saying the opposite and whatever else.