> made an educated guess
Grandparent deleted their post, but, assuming they just said "they correlated across IP" -- it's actually easy to guess, since the snoop would be able to detect and ignore a NAT IP -- it would be accessing thousands of accounts.
AFAIK Google's SRE's are more fancy sysadmins than performance engineers. Sysadmins often have the keys to the kingdom, though one would hope a sysadmin on project X only has the keys to project X.