"I suppose my policy should be to ask all female clients without discrimination about menstrual care products."

Ask everyone, if it's a provision (MSA) that applies to them. Don't you have a questionnaire? Focus on the MSA first, to avoid unnecessary queries. But then, you ask everyone. Not just female-in-appearance and young-adultish. The IRS explains qualified spending by any party:

https://www.irs.gov/instructions/i8853#en_US_2023_publink24188ld0e1123

"Qualified medical expenses are those incurred by the account holder or the account holder's spouse or dependent(s). Amounts paid for menstrual care products shall be treated as paid for medical care."

"Line 7

In general, include on line 7 distributions from all Archer MSAs in 2023 that were used for the qualified medical expenses (see Qualified Medical Expenses, earlier) of:

• Yourself and your spouse;
• All your dependents; and
• Any person who would be your dependent except that:
  • The person filed a joint return;
  • The person had gross income of $4,700 or more; or
  • You, or your spouse if filing jointly, are dependents of someone else."