Hi @kofa, thank you for sharing this experiment. Color management and ICC profiles are confusing so it makes sense to probe things like this to gain an understanding.
Personally I kind of expected this result. Elle Stone’s profiles from the repo you linked are matrix profiles and as such don’t contain any intent look-up tables (LUTs). It is also stated on Elle’s page:
As a very relevant aside, using perceptual intent when converting to sRGB for photographic image editing does not magically makes otherwise out of gamut colors fit inside the sRGB color gamut! The standard sRGB color space (along with all the other the RGB profiles provided in my profile pack) is a matrix profile, and matrix profiles don’t have perceptual intent tables.
There’s a special v4 sRGB profile available from ICC here that contains a look-up table for the perceptual intent. Might be interesting to see the experiment repeated with that as the output profile. It would seem to me, though, that in order to correctly apply the v4 output profile, the source profile would also have to be a v4 profile. More information in this white paper. The last chapter would seem to be the most relevant one.