Because this module is relatively new, and perhaps some users already learnt and get used to it, especially when it’s their first time use a colour balance to colour grade a photo, I guess not many will notice the difference (it’s just my opinion, sorry if I’m wrong), how about an adding experimental feature so that user can try and give their input of which one is more intuitive to use?
Personally, I’ve got no issue with current behaviour, but now that you mention it, I’m curious about how to use it in bare RGB. So either way is fine for me.
*edit: now that I look at it again in resolve, I forgot the luminance mixer is also adjustable near the colour wheel, so I guess it always works in YRGB, and I occasionally adjust the mixer to zero or 100 (or in between) depending on the task. Kinda like normalize channel in colour calibration/mixer.