There is no way 50% of the realism coming from the Fstorm community is because of the tone mapping. Install Fstorm and try it. See if your images look 50% more realistic just like that. They won't.
But the fact that so many people think that so much of Fstorm's realism is because of tonemapping, does not make sense. The fact that you estimate that Fstorm is more realistic 50% thanks to tonemapping is evidence of that.
You yourself claimed you are not an experienced Fstorm user - I am a very experienced dual user of both Corona and Fstorm (along with other engines). As mentioned in my last post I exclusively use Fstorm for high end product vis. Why? Because due to testing both engines extensively on many scenes back and forth, some even with very basic materials, the result is always poorer in Corona (and no, this isn't down in part to DOF settings, material conversion or a lack of knowledge of non "out of the box" Corona settings). It
is down to tonemapping and how highlights and blacks are handled by each engine. I have tried for days in some circumstances to match the image in Corona and the same ultra-photographic result simply was not possible
within Corona's VFB no matter any combo of curve adjustments, contrast tweaking, HC tweaking, Kim Luts, various other LUTS, Dubcats settings e.t.c. I'm simply not willing to go "yeah that looks pretty close", which might suffice for some.
Again, look at your own example (attached). Highlights have been visibly ruined and the wood tones are off and not reacting correctly as they should IRL - an observation I went into in detail previously. The average viewer may not spot this but in detailed viewing it is clearly apparent. If you don't think this affects overall photorealism, or certain edge cases in visuals in any meaningful way (would you concede to
some degree?) then I don't know what to say to you.
Why am I bringing up Fstorm? Because out of all of the render engines I've used it simply produces the most true-to-life images possible right now (and yes, it requires settings tweaking just like every other engine, so it's not a case of n00bish "hurr muh default settings" user error). The tonal balance of the image one is able to get out of Fstorm is
always superior, and I'm no Fstorm fanboy either - I wouldn't use it if I didn't have to, I would love to use Corona for everything due to it's superior feature set.
If not for tonemapping, what else do you think contributes to Fstorms superior photorealism? I've already mentioned several times on the forums better bitmap filtering/sharpness, bump mapping implementation, colour handling, pleasing noise patterns, and better DOF speed/sampling - however most of these can be worked around within Corona, Tonemapping however cannot be as it stands. Hence my prior statement of 50% (which was a fast and loose approximation, not verbatim gospel) - put a highly experienced user of both engines to work on the same scene in both engines, work around the quirks of both Corona and Fstorm, and the Fstorm image will be more photographic and pleasing to look at, fact. Case in point: look at anything Bertrand Benoit has produced (who I think most would regard as one of the best in the game that uses many different rendering engines), and compare to his Fstorm renders, and this was with his first trial of the engine:
https://bertrand-benoit.com/blog/westkaai-via-fstorm/ there is always something "off" about his photo realistic Corona and Vray renders (a minor uncanny valley effect, i.e lacking in brain fooling
true photorealism).
Side note: Fstorm as a rendering engine in general is terrible in some real world use cases; interiors with a lot of bounced light where it's annoying portal system will not save you. And not to mention VRAM limitations. It's lack of material and plugin support is also shocking (still doesn't have proper composite maps and multi-layered materials) - another reason I don't use it for anything more complex than product vis.