All the rules in https://skywater-pdk.readthedocs.io/en/main/rules/periphery.html#capm are "N/A" ... it would be nice if they were actually filled with valid values ...

Yes, wouldn't it? . . . At the moment, though, this is between Google and SkyWater, and I don't think that anyone at either place considers it an action item.

Is there still someone at Google even working on this ?

Aaron Cunningham took over the project from Tim Ansell, and my understanding is that Google is trying to offload the whole thing onto Chips Alliance. And that is the total extent of my knowledge about it.