Not impossible, but pretty hard.

Not so hard to defeat such sensors by making a matching product (which should be the goal anyway for printer ink). It would then be an arms race with third party vendors and your own internal ink and sensors to make a more consistent product yourself with better and better sensors.

It's possible to design print heads that are warped over time by ink that's not exactly like the official ink. At least, that's what I suspect killed my last (literally) Canon inkjet. There are a lot of rumours online about that practice.

And that would be entirely acceptable, perhaps even desirable, since it would be only be verifying the quality of the Ink rather than locking out competition even when the competition has a product of sufficient (or even superior) quality.