Sure, the 115" will be perceptually brighter than the 15.5" monitor, but it's still substandard for a bright environment. That's MY point.
That's the thing. Your point doesn't land. You take measure of brightness in very specific test scenario and you try to apply it for different scenario.
Image scenario. You have a candle which outputs say 10W as photons because imo that should be the real measure not nits. Now imagine scenario where you have 1000 arranged in plane as TV candles that output 5W each. You are in bright normal day room.
Question of those two scenes we pictured which do you think will be blinding and which will be barely seen ?
Nits comparison makes sense when you compare them to same size of monitor or TV. Like this monitor is 27' and it is 1000nits max and this monitor is 27' and it is 1500nits. The 1500 one WILL be brighter. But if you compare 1000nits 27' monitor and 500 nits 113tv the tv one will appear much brighter despite the fact that on spec shit it should be only half as bright, because share volume of photons created increases apparent brightness because that was brightness is, more photons hitting your eye.
That's the same reason why my phone Razr60 ultra can hit 4000nits on screen in hdr content never beets my g5 which can do max 2500nits because sure it is super bright but there is simply not enough volume of photons to hit retina like with big tv. The single pixel on TV is like several times larger producing much more photons than single pixel on phone. Which is why whole room is bathed in light at night with tv and not with a small phone screen.
It is literally the same principle why at night things become brighter. Not just because eye accomodation but also because there are no other source of photos to mix with photons that hit your eye and dilute original brightness.
This works with eye accommodation to protect your eyes which is one of key ingredients in perceiving if something is bright or not. If you are sitting before 1000 5w candles you are literally blinded by light unlike 10w scenario.
Nits are great measure to compare apples to apples not apples to oranges. 1000nits 20 inch monitor =/= 1000 nits 65inch tv.
Where nits matter is in highlights, those 1-10% window you often see in reviews. That's where it matters because it is angle of object that matters there not total volume. Aka the difference between shadowed area and very bright area on screen. In those kind of conditions nits matter.