I agree with the dif temperatures extracting the optimal hop oils, but I won't fret it if I'm not able to chill my wort down to 69c to do a whirlpool (If u use plate chillers).
Considering that breweries deal with MUCH larger qty than ours, I doubt that they whirlpool anywhere lower than 90-95c. With some hops, i get quite a noticeable amounts of flavour coming through even at 60mins addition. I see it like enzymes in the mash, your beta-amalyse are still working at 67c and it's doesn't denature instantly. Yes, you lose a certain amount of aroma if you whirlpool hot, but the quality of the hops make a bigger difference than the temperature of the whirlpool. Not to mention that most of us here add a crazy amount of whirlpool hops, so I think that you will gain more aroma with that huge quantity than what you will lose whirlpool at 95-100c. Then again, where is the point of diminishing returns with regards to whirlpool/flame out addition? Where is the point where it's out of our threshold to taste?
I used to chill my wort down to 80c before addition my whirlpool hops, as I wanted to stop isomerising AA. I would add my 60mins/15-0mins to achieve my intended IBU, and then add my aroma hops at 80c and do a whirlpool. I used 345gms in the kettle for a 6 gallon batch of DIPA and another 190 gms of dry hop.
Of late, I've been starting to switch to 30 mins whirlpool at flame out for better hop utilisation and it does save me alot of hops!! The late hops aroma is very delicate and amazing, and can be overpowered if you aggressively dry hop. That's one of the reasons why i'm adopting this approach, along with a chance I'll strike lottery and go pro, then I'll have to adopt this method!
Coming back, you will get better extraction with a whirlpool than just flame out addition, purely due to agitation. Just like steeping a tea bag in hot water, with and without agitation.
Some breweries have a whirlpool built into their kettle, but the BIG ones usually have a separate whirlpool vessel.
To be honest, I've not done enough brews with this new process, but the initial response to far is a cleaner hop aroma/flavour without being muddy. I'm also trying to master this because I wanna add about 1.5-2lbs/bbl of whirlpool hops for certain beers, but that may give too much BU and end up with a 130ibu beer!