Part of the car test was reversing so a vehicle without reverse would not be any use to take the test. I do not know when the rules changed, but over the years they have got more and more tied up in respect of the anachronistic vehicles that still exist in small numbers, but do not really fit in any category.
Interestingly an IC was not a car, so a separate system. Now DVLA say they are PLG, you can drive them! Logic, always sacrificial to bureaucratic expediency.
PSV was an oddity. Up to 12 people, but not paying passengers. That was changed after several bad accidents to a full PSV license. It was then you needed to apply for old fogeys rights, or you lost them. However it remains the case I cannot drive a bus for reward.
I never bothered with a bike license as I am bloody useless on a bike. It is why I got into Trikes when my mates went biking. Several into racing, I lost touch with most, not surprisingly. I passed my test in a Datsun Cherry.