A suspended user cannot login to the Discourse site. If a user attempts to login to a site with their username and password, they’re denied access. The user’s “last seen” time is not modified.
However, if a suspended user attempts to log in with a social login (Google, Facebook, etc.), the “last seen” time is bumped to the current time, despite the user being denied access. This is inconsistent and would be nice to fix. #pr-welcome