Now getting a refund from Google Play Drive Storage, although we are still able to add files to Drive. Very very weird order of actions, as we still don't have Pooled Storage.

Split / partial licensing answer from Google support engineer: *** The partial domain licensing can be added only when the costumes have 100 seats and at least 15 of them should be on a higher SKU. ***

I thought the old ways of increasing storage were discontinued, but I was wrong. Perhaps it's an option for those few of your users for these couple of months until Pooled Storage has actually been rolled our?

Same boat here. Google Support mentioned in our ongoing ticket-thread that "Pooled storage will be enabled for your Google Workspace Business Starter subscription in the coming weeks with new admin controls." actually means "...coming months with Q1 ...