This is my anecdotal experience with full sun...
As a M E, an analogy I can relate to...
An engine can not achieve full throttle HP unless every support system is 100%. If the fuel filter is clogged the engine will run lean at full throttle maybe miss firing and possibly lean detonate to death. If the air filter is clogged not supplying the engine with air it needs to go full throttle it will run too rich and won't be able to achieve full throttle power, maybe bucking and surging.
A plant is like an engine in some ways. It needs its roots to be able to fully absorb and thus supply water, nutrients, and to be able to breath. A plant also needs sun to complete photosynthesis. Just like an engine it needs these things in the correct proportions to achieve 'full throttle', full sun, to achieve maximum growth/production.
Full throttle on an engine is achieved by allowing full fuel/air into engine. Full throttle growth/production on plants is achieved by the roots being able to supply enough to satisfy the foliage full sun absorption/photosynthesis.
Its true, some plant species can't take the mid day high uv/temps/duration of southern/sub tropics/tropics, even if everything is 100% correct. Some can and thrive in it...
I have found on some plant strains that normally can take full sun, will wilt/not do well in a couple few hours time under full summer sun. Not having even slightly compacted media is a biggie. But, after a transplant to larger container and fresh, properly constructed media for its particular environment, in just a week or 2 that plant can now take full sun all day long and thrive with outrageous production....
I've seen this many times. Also have seen that a transplant doesn't help at all. Upon further investigation by washing off the root ball, have found root pests have part destroyed the roots.
My point being, most all the Caribbean pepper strains, most all Chinese, and annuums can take the full summer sun here in sFL when everything is perfect. Perfect media, perfect watering, perfect nuets, perfect root development, no pests, etc. Just like an engine, all systems need to be perfect to use full fuel/sun.
About baccutum, in my experience even when all is perfect, they might not wilt a lot, but don't seem to do well in full sFL summer sun no matter what I've tried, and I've tried. I've concluded Baccutums being from mountainous areas of Peru high elevations do get high uv, but not the high heat/humidity, or duration in there mtn terrain.
They do much better for me under my sun filter or shade cloth. But in the doldrums of mid summer high heat/uv/humidity, they seem to slow down even under shade cloth. But still produce ok.
Otoh, my mature fully hardened off Chinense, luv full sun once everything is right in the roots/media. They thrive in full sun for me, producing hundreds of sweet hot juicy pods all thru out summer....
So in my experience/opinion, for me, using shade cloth for mature hardened off fully, Chinense, like a Carolina Reaper or BT Scorpion, so it doesn't wilt in mid day sun,, is more or less a band-aide for some level of other short comings I've missed...
jmo