The decision to merge all the ratings was apparently made by a ~15 kyu player with this logic:
I don’t think that’s a valid opinion at all.
There’s also this option from an old post if all else fails. I don’t think OGS needs to do this though:
Any worries about UI inconsistencies can be fixed with better UI design or frontend development. At the core ideologically, it simply doesn’t make sense to equate 9x9 rating to 19x19 rating. I’ve always been weaker by a few stones at 9x9 than 19x19 for at least 10 years, because I never cared to study corner life-and-death situations or 9x9 theory. And for a long time on OGS, I was 3-4 dan at 13x13 but it took me a lot of effort to reach 3 dan or even maintain 2 dan on 19x19, because the opening I used for 13x13 was not as effective for 19x19 and I didn’t know how to use influence or how to evaluate who is ahead/behind in points on the bigger board. It gave me a mild case of imposter syndrome.