Sinks, showers, pipes - usually pertaining to water or sewage. So don't mix them up.
Forgot to mention something. I filled a 5 gallon bucket TWICE and poured the entire contents of that down the toilet. I never saw any evidence of water leaking from under the toilet. Other than aggressive plunging, I can't think of a more difficult stress test for that seal.
Wow, it is still dry. Did I actually fix this? It would appear so. I still don't know 100% if the wax ring was ever an issue. Maybe it was. But the shutoff valve was ALSO an issue as the old one was DEFINITELY leaking. That Fluidmaster better-than-wax ring and new shutoff valve are not leaking. Yay.