I accept your observation and would like to clarify/elaborate on my previous comment. If a pilot develops a medical condition that prohibits flying based on an FAA Certificate (e.g., ever having had a kidney stone), then they may no longer perform crewmember duties (unless they get a Special Issuance.)
AIM 8-1-1 (a) (3)
Caution: The CFRs prohibit a pilot who possesses a current medical certificate from performing crewmember duties while the pilot has a known medical condition or increase of a known medical condition that would make the pilot unable to meet the standards for the medical certificate.
On the other hand, if they have not had their medical certificate revoked nor a new application denied, then they may fly under Basic Med as long as "not aware of any medical condition, as presently treated, could prevent the individual's ability to safely operate an aircraft" (e.g., the kidney stone has passed).
FAA 8700-2 Comprehensive Medical Examination Checklist:
The most recent medical certificate held (including an authorization for a special issuance certificate) must have not been denied, suspended, revoked, or withdrawn.
As far as I am aware, the FAA does not hunt down every airman's current medical records and issue revocations. They will deny a renewal application if there is a disqualifying condition disclosed in the process, hence my original admonition to not make any new applications. In other words, there is a difference between developing a medical condition that renders the FAA certificate no longer applicable, versus having the FAA actually revoke/deny said certificate and thus go through administrative hell to get it back (been there; done that). In the former, you go get Basic Med. In the latter, you have to get a Special Issuance.
In all cases, it's up to the pilot to be honest with themself and not fly if not safe. Basic Med is advisory, FAR Part 67 is administrative in the way that this is implemented.
hope that helps,
-dbh