I agree that it would break the FIDE rules against note taking, but this is not a FIDE tournament; it is online blitz on Lichess, so FIDE rules need not apply. You'd have to look at the Lichess terms of service instead. They say
- Cheating. We define this as using any external assistance to strengthen your knowledge and, or, calculation ability to gain an unfair advantage over your opponent. Some examples would include computer engine assistance, opening books (except for correspondence games), endgame tablebases, and asking another player for help, although these aren’t the only things we would consider cheating.
The definition is open-ended so it's really up to the Lichess administrators to interpret. Does drawing an arrow on the board during a blitz game "strengthen your calculation ability?". Perhaps, but one could also argue that it makes you waste precious time, so it is probably more of a handicap than anything else. More importantly, just the fact that the Lichess user interface supports drawing arrows during a game (something which I had never noticed, despite being a frequent user!) may reasonably be interpreted as implying that the administrators approve of that use.
I don't think the "banterers" who stream their games draw arrows as a calculation aid, but rather to communicate their ideas to their audience. I'd love to hear from anyone who uses this feature and finds it helpful while playing blitz for non-streaming purposes. (Arrows might be more useful for correspondence chess, but there you are definitely allowed to use analysis boards, opening books, notes, etc., so arrows shouldn't be a problem.)