The issue isn't the flight - over 12's can fly on their own - but as you've seen it's the hotel element - and being able to book it - that is the restriction.
Have people bought a holiday and not used the car or hotel element then yes but the examples we see on here involve adults so the booking meets the restrictions (there may be <18s on the booking but that's not the same as what you want to do).
BAH won't knowingly do a booking that they know does not meet the hotel requirements.