I share your frustration.
Basically they must just tick boxes in response to your answers and tot them up at the end, but apply no logic. Like you, I can only drive one car at a time and only want myself as driver so it's not like your using the second car policy for "fronting" a young inexperienced driver.
I have a "normal" everyday car for which I pay �260 fully comp. I have bought a 16 year old which has very low mileage and is already regarded as a future classic. One of the leading "Classic car insurers has just quoted me �360 for TPF for 3000 miles and it has to be garaged.
And yet the banner on their website boast how Mr X insured his Spitfire for �120 or something.