Did you get any further with this? I’ve also noticed the lack of difference between the 3 rendering intents, at least using sRGB (websafe). I started using the sRGB v4 Preference Perceptual Intent (with LCMS in preferences) from here -
(International Color Consortium site)
Here is a checker shot with the saturation ramped up showing a difference between perceptual and relative colorimetric as set in Output Color Profile module.
