[JLMounce]

It's my understanding that the replaceable cartridge is more about modularity between parts and being able to provide a higher quality lifter, with better tolerances at scale over many different skus.

With the central cartridge being the "functional" part of the hydraulic lifter, they can build for more platforms with less tooling, in a more precise fashion.

As far as when or why you would need to replace the cartridge, if you had a lifter that had a poor bleed down rate, you could replace the cartridge instead of the entire lifter. Or, if you had a bearing failure, you could replace the cartridges and possibly clean the body/roller. I agree primarily the replaceable nature isn't a huge selling point. I think that's more of a them thing that helps keep quality up and costs down.