I think you overestimate how far apps are willing to go for stupid reasons.
Also, there is still the DEVICE_INTEGRITY check that verifies the hardware side of things so if old devices have to be pushed, app developers still won't let you run their apps on LineageOS
I'm sure they are stupid but they already have some trouble to justify to their customers that they can't run the app on Android 11 so phasing out actual brand new devices that customers have is going to go a bit too far for them.