Video here:
https://www.youtube.com/watch?v=1-f7YNxBjV0&list=LL
It's mostly worth watching, but it can be summed up in about a sentence. The sentence the video person would use is the wrong one, so I'm not giving you his. I'm giving you mine.
That sentence is, it's for the best if you as a DM actually explain what is going on in the field, even if everyone already knows, after each action taken. It paints a better visual picture in the mind's eye, and that is necessary for both MoaM and even TotM play. I learned this lesson in the 90s from a veteran AD&D1E player running AD&D2E for my first ever group. He did it like it was second nature, explaining and acting out every action taken in combat back to the people who took it. While it does often take a bit longer, it paints the picture a lot better than otherwise. Now thirty years later, the only real thing I remember about these sessions other than generalities of plot were specifically my DM acting out various actions each party member was taking. That's how much of an impact it makes.
The video is correct in that this should be done, is The Right Way. It is incorrect as to why. To be fair, video-person is framing the rationale behind what he thinks is important in RPGs - the story, plot, background, character "agency", yadda yadda. All that 5E-6E garbage that I have no business talking about because I don't care.
What it's really about is explaining the state of the battlefield. If you say "your arrow misses widely, skittering off cobblestones into the dark" or "your arrow is deflected off the enemy's armor" or "your arrow narrowly misses and lodges itself in a nearby support beam" or "your arrow lodges in the enemy's shield" These are not interchangeable statements. The first statement is for someone who rolls a 2-4. The second is for someone who rolls >10, < AC of opponent. The third is for someone who rolls a 9 or 10. The fourth is for someone who fails to hit AC by exactly 1. You're literally describing what happened qualitatively. The word "miss" is not the problem that the video person thinks, the fact that there is no better explanation provided of HOW the miss occurred is.
Hits also need similar descriptions. Lighter hits are scratches, cuts, dents, minor wounds. Heavier hits are more brutal, especially if you get over a milestone generally when half enemy HP is gone, and again at <10% HP left (or <2 HD left for bigger monsters). If a full HP Orc at 8 HP takes a hit that does 1 damage, that's a scratch or minor bruise. If he takes another that does 4, that's a palpable hit and he's looking the worse for wear. Another hit for 3 and "he's on his last legs, shaken and soaking in blood". This gives the PCs a state check without giving them HP information. Practically every enemy should be like this, other than perhaps undead or aberrations behind human understanding. If it's squishy and bleeds you should be able to describe how it's squished and bleeding.
Players should also keep meta-talk out of the game, and try to describe their own conditions after the fact. In old D&D PCs max out at ~9HD and get less bonus HP from Con (and it stops at 9th level), so it's less likely you'll have pincushion PCs with (comically) 15 active wounds at any given time.
