As someone who is learning to read and transcribe, this was an interesting video. I am in the SteveCS camp here. There is an Anthony Wellington video somewhere where he talks about writing as a way of learning to read, which I completely agree with. Learning songs by ear is fairly easy. Obviously the harder the song, the longer it takes. But there are only so many notes, so you will get there. I think the majority of people have good ears even if they dont know they do. In fact, sing a short passage to most people and they can sing it back. Only the truly tone deaf would likely struggle with that. So, really, what have you trained? IMO, not much. You are doing something that humans can naturally do without much struggle. Then fumble around on the instrument and find the note.
But now try writing that down... wow, different ballgame all together! Now you need to know the key, so you need understand key signatures for the score, and you need to understand the rhythm and how to write that out. Is that a dotted 16th there? 8th note? OK, now my brain is working.
Committing to memory - again, for me personally at least, is easy. Almost impossible NOT to remember a song I have played a few times. But hey, if I forget, I just look at my score. When I was younger and had piano lessons, my teacher would stop me mid-song, point to the score, and say "where are you?". Of course I would have no idea as I was playing from memory. She was always envious that I could remember a piece without looking at the sheet music. She leaned too heavily on sight-reading, so I do understand your point there.
My goal is not to be able to take any piece of music for bass, cold, and play it. I dont need to take reading to that level. But what I do need and want, is to be able to learn any song from a score without ever hearing it. IMO, learning that skill is greatly expedited by transcribing. As Anthony says "If you can write it, you can read it".