Regarding the OP question - are you trying to apply logic here?? to a CODE???!!!
There is no logical reason to prohibit the required amount of water closets to be met via a bunch of unisex one-holers. They have invented this really cool device that keeps people from barging in on an occupied toilet room. It's called a Lock.
In Healthcare, it is very common to have a bunch of unisex one-holers spread around patient and staff areas so patients don't have to carry a cup full of "Bud Light" from the lobby area and staff don't have to leave their unit. Fortunately, most AHJ's I have dealt with accept those one-holers as contributing towards the required fixture count. Good on ya, AHJs with common sense. However, I agree that it is not in accordance with code.
Regarding 2012 403.2.1, they didn't help matters here. The language is what you would expect from a committee. To 100's point, there is nothing in the code that requires each "toilet facility" to have only one water closet. The code requires x amount of WC per BUILDING or TENANT SPACE. It would have been so easy to just say "Where a building or tenant space requires a separate toilet facility for each sex and each BUILDING OR TENANT SPACE is required to have only TWO water closetS,..." But they didn't. So it is up to you guys to figure it out. I would say the intent is what I re-wrote. In other words, it's only in really small spaces, that otherwise would have had one men's WC and one women's WC that you can make em unisex. It is still prohibited (by code, not common sense) to have 30 unisex one-holers. And I mean prohibited, not just not applying towards the required count.
And dammit, I mean unisex, not family/assisted! It has always seemed silly to be standing in a line consisting of only one gender outside of two single-holers when the "other" gender's toilet room is empty. So maybe one person is put off by a funny looking receptacle next to the WC, or another person is put off by a urinal they are not equipped to use, but why is that CODE?