> If lenovo is buying a billion chips a year, why can’t they lock in like Apple?

Lenovo controls less of the stack than Apple: CPUs (Intel/AMD), BIOS, operating system, etc. While ostensibly Apple and Lenovo are both selling personal computers, Lenovo is in a (sub-)segment of the market that is commoditized with Dell, HP, etc.

If you need to run Windows and associated (Windows-only) apps, what's special between Lenovo/Dell EMC/HP/etc? How much of a difference is there between Coke and Pepsi?

A lot of vendors hitched their wagon to the Wintel duopoly, and now they're all riding (or being ridden) herd.