That's still 2 orders of magnitude smaller than the scale of Figma—they would need to somehow manage millions of Postgres schemas. I don't think it's a realistic possibility
Sounds like this is just normal sharding. Completely different from having a totally separate schema like GP proposes (with that approach you don't use sharding keys at all).
But I do see now, searching for that part of the info specifically, they mention
Peppy Peppers’ orders can be migrated by running SELECT FROM orders WHERE shop_id = 1 FOR UPDATE on Pod 1’s database