So I understand the whirlpool and that if a commercial brewery is doing a flameout addition, a homebrewer with an immersion chiller that's not doing a whirlpool (like me) should treat it like a 20 minute addition.

But does this mean that commercial brewers really aren't doing "flame out" additions? Most homebrew recipes have a late hop addition at 10, 5 or even zero minutes. How does a commercial brewery do those late hop additions? Do they add them with x number of minutes left in the whirlpool?

Also, if I do want to do a whirlpool, at flameout, should i just stir my wort for a few minutes - let it settle (total time 20 min) and then drop in my immersion chiller? Or should I not even bother? I'm mostly interest in the whirlpool for the break separation. But what's the point of whirlpooling before chilling then? The cold break will not have separated yet.

I think most commercial breweries do late hop additions, flameout additions as well as whirlpool additions. I would guess that they take the whirlpool time into account, and adjust their recipes. For example they might add more late hops and do no whirlpool addition to compensate or they might add less late hops and then do some sort of addition in the whirlpool.

The point of a "hot" whirlpool is to remove hot break and hop debris before the wort is sent through a plate chiller. If a pro brewer wants to remove any cold break they probably do this after they have transferred to a conical fermenter where they can dump from the bottom.