> The iOS device line gradually shifts towards the M chips

No it doesn't - no iOS device has ever shipped with an M series chip...

> Isn’t the M line is more performant and energy efficient comparing to the A chip?

Yes to A, no to B.

Also, you're completely leaving out scale and cost. Apple has already made (ok, had TSMC make) hundreds of millions of A18 chips, so throwing an A18 pro in their least expensive laptop ever makes a lot of sense.

Yes, the iPad Air and Pro all come with M chips.