UserLoginFailure log username in SubjectId column instead of userid

[BerDuc]

If you test a user login failure, in the AuditEntries table you will have the username both in the column SubjectIdentifier and in the column Subject. For all the other events I have a numerical identifier in the SubjectIdentifier column, so it feels weird having a username for the UserLoginFailure Event.
I searched why and found that in the UserLoginFailureEventAdapter, the line 16 look like this:
16 public ResourceActor Actor => new ResourceActor(ResourceActor.UserSubjectType, evt.Username, evt.Username);
It feels it is a mistake logging two times the Username. Is it by design? if so, why?