That is interesting. There is some magic networking going on if Google allows every customer to allocate an IP range of their choice, and the customer can use all the IPs in that range, and Google runs multiple customers on the same network (same VPC and subnet).

A project can contain multiple VPCs. And a VPC can contain multiple subnets, but not with overlapping ranges.

https://cloud.google.com/sql/docs/mysql/configure-private-se...