I also don't understand: "My guy now has to apparently pay twice for Medicare, it seems."

If the person has not got a job, they are not paying twice.

If a person is self-employed, they are allowed to take medical insurance cost as part of business deduction (within limits), which gives them parity to the employer/employee provision.

If a person is on Medicare, they are paying premiums, and Part B is priced according to their income (there is a two year lookback). That still is not twice.

Itemized Deductions need to exceed the standard deduction, to show on the tax return as a deduction. It's one or the other.

The medical section of that schedule has a floor or limit, which has had to exceed 7.5% (or 10% of AGI, for most of these past few years, and changed in consideration of the pandemic hardships that arose). You will want to know that threshold for the year you are working on, to know if their medical premiums, medical care, and other costs even meet that reporting threshold. They might not exceed this limit, and don't even contribute to the rest of that schedule.

This topic should be a good reference for you:

https://www.irs.gov/taxtopics/tc502

Because you should understand this better, and be able to communicate to your client without the melodrama. They rely on you to assure them things are going well.