A very valid take on spec writing. It sometimes feels like the research on formal verification is like the drunkard searching under the lamppost, in that the target is often a domain which is itself well-suited to a particular kind of computer science being done on it.
However, I think there is a middle ground between the "naturally verifiable" and the difficult cases. Certain domains, like banking apps, can want correctness guarantees about UI behaviour. A closed-off app can be very normative, so in theory specs like "the user did this action and confirmed it" can be made meaningful. But tying specs to UI is a tricky thing, and it's clearly volatile in a way function boundaries are not - apps go through redesigns, styles and elements move, etc. The abstraction of a UI as a state machine isn't hard to imagine, but actually hooking a spec into the program is a problem unto itself, and the common response is to simply ignore these problematic domains and do something easier like a backend spec that doesn't have to deal with the questions that aren't PL-shaped.
However, I think there is a middle ground between the "naturally verifiable" and the difficult cases. Certain domains, like banking apps, can want correctness guarantees about UI behaviour. A closed-off app can be very normative, so in theory specs like "the user did this action and confirmed it" can be made meaningful. But tying specs to UI is a tricky thing, and it's clearly volatile in a way function boundaries are not - apps go through redesigns, styles and elements move, etc. The abstraction of a UI as a state machine isn't hard to imagine, but actually hooking a spec into the program is a problem unto itself, and the common response is to simply ignore these problematic domains and do something easier like a backend spec that doesn't have to deal with the questions that aren't PL-shaped.