It seems to mean one can legitimately buy the option to use the radio as a test tool or for other legitimate uses, as
@kd4efm said. The legalese may have some problems though.
Federal/NTIA rules are different than FCC, as you've noticed.
The FCC Part 90 rules are exceedingly clear on this, as are the other rule sections. Average Joe radio user should not have the ability to change the function of the radio. Having FPP active technically violates the certification of the radio in many services. I think that's one of the reasons you'll find it buried, controlled by password, or otherwise difficult to activate.
Yeah, pretty much every fire agency ignores that. We had a bunch of JT1000's at work for a while. The FPP dongle sort of kept most of it under control.
Just about every radio tech I know has their radio set up for FPP. It's just too handy a tool to not have on site if you are testing something.
That being said, Deputy Fife or Ralph Kramden driving the bus don't need access to it. Radio end users don't need access to it. Most people don't need access to it.
It should be hard to get, harder than it is. I had to go through multiple steps to get wide band turned on a few radios at work, including signing papers saying I understood the FCC rules. Same needs to be done for FPP.