.well-known/security is listed as a prominent example, but is not in the well-known category.

Useful reference https://securitytxt.org/

Though some sites drop it at the root /security.txt instead of /.well-known/security.txt

Note, invites beg bounties spam.

It's in the "Security" category. I guess whatever categorization scheme they're using doesn't allow assigning multiple categories per item.