A freaking brilliant piece of filmmaking (including the Prokofiev Capulet and Montague excerpts), not to mention wise advice.
I think there are at least 2 types of reader for a script that hasn't been filmed: (1) gatekeepers who are looking for a script to recommend / film; (2) everyone / anyone working on a script that has been sold and is about to be filmed. (Of course the following speculation is based on common sense rather than real-world experience with the vetting and filming process.)
Avoiding an offense to the hypothetical script evaluator informs most of the "thou shalt not" advice, e.g. breaking the illusion that the gatekeeper is watching a movie, rather than reading a script. I can't speak for other readers (I was never a gatekeeper), but I think anyone familiar with script format reads with two consciousnesses--(a) evaluating what's on the page, including style, voice, professionalism, etc.; and (b) being immersed in the audio-visual world of the story as if it were a film. I don't think it's a major crime to pull the gatekeeper out of the illusion, since gatekeepers are always aware that they are reading a script to be evaluated. On the other hand, any bending or breaking of so-called rules that signals that the writer is a writer and not a storyteller won't help sell the script--these infractions can spoil the reader's enjoyment, much as a missed note by a professional musician at a concert can ruin a trained musician's pleasure. I agree with Stokes' objections and his ranking of seriousness--I can't imagine an unknown writer scoring any points with a gatekeeper by using "we see" / "we hear."
BUT someone who has sold the script or is filming the script herself / himself may use "we see" as some sort of hint to the people acting / photographing / etc. the script. I can think of only one example that worked (but I haven't read enough filmed scripts to make a final judgment), the first three lines of Big Fish:
...
A RIVER.
We’re underwater, watching a fat catfish swim along.
This is The Beast.
...
One of the major themes of the story is the power of imagination and surprise over a materialistic, rational, self-limiting perspective. So it makes perfect sense for August to take the reader out of the "what's on the page" literalism into a shared, fantastic immersion. This is not lazy writing, it's purposeful, magical writing. So any writer who has already passed through the gatekeepers and can write like John August should be lauded for doing so whenever the strategy works. This is not a "So-and-so did it, so why can't I?" It's an "If you can write like So-and-so, but without seeming to imitate So-and-so, then you may want to go for it" (keeping in mind that you're more likely to get away with it in a shooting script rather than a spec).
But there's another problem too: when advisors use a simple "thou shalt not" prescription, they reduce the wonder of storytelling (which is what the unsold writer should be concentrating on) to a simplistic paint-by-numbers gambit. Jonathan Stokes obviously doesn't do this--I'm looking forward to watching the rest of his installments. Thank you for the wonderful discovery.