I would assume when you play an arranger keyboard you are composing songs don't you agree?
Admittedly, I have not watched the video because the thread title didn't interest me that much.
And, no, I don't agree that I am composing a song when playing an arranger KB, because I am playing a song someone else composed ... Even if I am taking an ad-lib solo, I am using the composer's song as my basis ... JMHO