Apple is not "just using arm chips". They have been designing their own 100% custom cores for more than a decade.
But come on - if they had to use intel’s fab - their chips would be terrible. The reason the m6 is faster is largely because TSMC invented a smaller process node.
If they made it on the same node as last time it Would basically be the same speed.
Apple are not wizards. They did the bulk of the work making m1 and the subsequent chips have just been on faster nodes
If they made the new m6 but with the fab tech from m1 how much faster do you think it would actually be? My guess is not much.