It’s just a question of efficiency. The first day sales of new ICE are outlawed there are going to be a large number of ICE cars already on the road which keeps most gas stations in business the next day. In effect the difference between 0% ICE or 10% ice is only visible several years in the future.
It’s simply bad policy to create a situation where a lot of 5-15 year old cars get scrapped because nobody can find a gas station. The country is much better off when people scrapping cars because they can’t get gas are doing that to 20+ year old cars.