I’m fairly certain that Model F and M keyboards are considered mechanical.
It’s not a precise category. But I’d even go so far as to say they are the type specimens for mechanical keyboards.
Yes, most products in the category use Cherry-type switches, but Topres are definitely considered mechanicals and they combine a rubber dome and a spring.
Literally all keyboards are mechanical, what’s the alternative? Organic?
The term is used figuratively, not literally.
Buckling spring keyboards count, rubber-dome and scissors don't. There's no overarching principle here, if there is, it's how they feel under your fingers.
I am typing this on a Model M that is dated "22JJUL88" - I do all of my important typing on these keyboards.
https://en.wikipedia.org/wiki/Model_M_keyboard