It’s perhaps not appreciated that the change from Adobe RGB to Wide Gamut colour processing space was a major change. What I think we are seeing is the expected fine tuning of the demosaicing/colour pipeline. Tone/tone curve impacts the colours we see and with Photolab things are perhaps more complicated than with most demosaic processes in that chromatic aberration, white point, colours etc are involved in the demosaicing process with PRIME/DeepPrime/DPXD.
Similar “changes” occurred in Adobe LR when they changed their raw “engine” or processing pipeline. You can always revert to “Legacy” colour space if it’s a problem, as we used to revert to previous raw “engine” versions in LR.
Personally, just looking at Photolab today, I feel it is getting better with each point release and I expect the changes to settle down once they have nailed down and optimised all of the variables involved. Best advice, as it was with LR, stick with the previous raw engine if backwards compatibility is vital for current projects. Again as with LR when you open old PL5 edits you will default to Legacy so no problem, although you probably can’t resist re-editing with the new raw engine for a better result 