The key bit is that it (sounds like) they use it only for identification, whereas the SSN in the US is treated as a "secret" which can be used for authenticatio

The key bit is that it (sounds like) they use it only for identification, whereas the SSN in the US is treated as a "secret" which can be used for authentication (!?). Thus a weird legal limbo where it's officially not supposed to be shared around, as it can prove who you are... yet all kinds of businesses are required to record it to identify their employees :|