It all made sense when I got my period this morning.
Side-note: Why do we use verbs like get, have, avoir (in French) for our periods (règles, in French, always plural & it literally means “rules”)? I don’t think you can really “have” “a period” because a “period” is something that is being shed, a lining that is discarded. It is a process in motion (blood coming out the vagina & running down legs) not a static object you possess.