A few people have mentioned the young and old women point, I don't quite understand that tbh. They will and have menstruated and that clearly isn't the point she's making.
Are you purposely being obtuse? If someone is using the phrase "people who menstruate" that is because they are talking about something directly relevant to menstruation. A study about menstruation and its effects on the body is in fact irrelevant to the very young and the very old. "Should we have supplies on hand for people who menstruate" means the very young and very old are not relevant to the discussion.
She's clearly referencing the point that biological men don't menstruate and never will and so shouldn't be included in that group
Which is why "people who menstruate" was used. The strawman is treating this like an attack on women instead of a more exact term for the specific people relevant.