I understand that the AS information plays a part in how addresses are populated in the new table for IPv4/IPv6 addresses, but how does it work for .onion addresses?

I understand the address assignment for IPv4/IPv6 via (https://github.com/bitcoin/bitcoin/blob/505ba3966562b10d6dd4162f3216a120c73a4edb/src/addrman.h#L57) but the process for .onion address is not clear to me. The only thing I know is that the group for the .onion address is the first 4 bytes of the address(without the .onion)