The Motorsport UK have updated the Road Rally tyre regulations.

3.2 For all Road, Navigation, Targa, Road and Historic Road Rallies tyres are free subject to the following.

a) Tyres on the current FIA List of Asphalt Eligible Tyres are permitted; including sizes not homologated.

b) Tyres on list 1B (from 2020) and 1C are not permitted, other than a few specific tyres for historic cars.

I sort of get the reasoning for banning list 1B and 1C tyres? But don't get the logic for permitting FIA molded slick stage rally tyres?