Most of this is right, but needs some things corrected.

LOS is kept up by individual maintainers of the devices, and so it can cover more of them. But that also means you expand your attack surface to lineage, maintainer, microg, etc. And that's just on supported devices. Unofficial devices are even more wild-west, having much delayed releases, OS updates, security updates, everything.

Not only that, but Lineage requires that you unlock your bootloader and often have your phone rooted to be able to do everything. This introduces special points of insecurity and possible issues in the future.

GOS is from a single source, for a single line of phones, and uses a designed method to load cryptographically signed ROMs onto the device, and then validate updates using the same method. The Play Services are sandboxed and disabled by default, so you can just never use them if you want. Overall, this makes for a more cohesive device. One that is more private and more secure. Especially so, when you can buy a new Pixel device and have guaranteed updates for as long as Google will do so for the same device.