Several customers do not use the samaccountname which I believe is what you mean by company_login. They use a GUID that AD provides for their account. This field is truly a unique identifier. Really company_login is being conflated for two purposes: a username login that can be used for ldap pass through and a true unique identifier that will not change ever. 

I think it could make sense to have those split to prevent confusion in the future and allow for both cases to happen.