This is what the Google Support Agent said when I asked about the 512GB and 256GB Pixel 6/PRO variants:
"Please understand that this has already been escalated to the product specialist. We don't have a tentative date yet but it will be available soon."
I kept pushing for an estimate gauge (e.g 1 week, 1 month, 5 month) but the support agent was unable to provide any info on that. Perhaps if more of us request for the local availability via their Live Chat (linked below) it would create an urgency for them to speed up the availability:
https://support.google.com/store/gethelp
So we've no clue what "available soon" truly means. Any speculations based off past pixel predecessors?