Do check that they're not using a "cheating" implementation, I think some DBs have "sequential UUIDs" which are either UUIDv1 the right way up (aka uuidv6) internally, or an other scheme which yields a sequence (e.g. mssql's NEWSEQUENTIALID).

Alternatively, it's possible that they created pseudo-UUIDv1 by hand putting data in UUIDv6.