I don't know the answer to this specifically, but there are several issues.
HSA accounts are individual accounts, not joint accounts, although it is possible to make all contributions to one HSA account if you have a family health insurance plan - in this case, you don't have two different people contributing - you have one person contributing on behalf of themselves and their spouse. A fine distinction. And apparently once someone turns 65, they can continue to contribute on behalf of their younger spouse.
And withdrawing is only done by whomever is named on the account. You can pay for medical bills for family members, and if you are over 65, you can withdraw funds for personal use, but you pay ordinary income tax on those withdrawals. Whether its for bills or
So - for each HSA account, only one person is making the contributions and the withdrawals.
Once one spouse reaches 65, it may make more sense for the younger spouse to have their own HSA account since they have different insurance now from their older spouse. In fact while both spouses are between 55 and 65, having separate HSA accounts allows each of them to take advantage of the catch up contribution.
I expect the younger spouse, if they have a separate HSA account, can't simply withdraw funds for their older spouse unless used to pay medical bills. I expect the younger spouse's age is used to determine whether withdrawals can be made without penalty. They apparently also can't pay for their spouses HSA eligible Medicare premiums until they themselves are 65 or older.
But I also ask whether it matters. Two married people filing jointly are treated as one tax entity. And the money is not being withdrawn tax-free, unless used to pay medical bills. So there is nothing to be gained by contributing and then withdrawing.
DH and I maintain separate insurance and separate HSA accounts (which means each of us can use the 55+ catch up contribution). To me this keeps things cleaner, and causes less disruption once someone reaches Medicare age and one spouse switches insurance. It's more flexible as well, because each spouse can have a different health insurance plan if they choose. Of course we can still pay for each other's HSA eligible medical expenses.
Some related issues here.
http://www.ifebp.org/inforequest/ifebp/0166103.pdf