I know for a fact that my Levoit unit isn't that sophisticated because when it asks you to replace the filter there's simply a button which resets the filter life back to 100% that you're supposed to press after changing it - if it were actually doing anything clever to determine the state of the filter then you wouldn't have to tell it that it's been replaced, it would be able to tell on its own. I suspect it's nothing more than a timer which triggers the warning after running for some hardcoded number of hours.

Can this machine know that?

A machine could, but is this machine sophisticated enough to do that? Why do we play around with hypotethical scenarious where this warning message on another device might not be shitty DRM?

Are you stating that this specific machine actually does this, or are you just theorycrafting that a hypothetical machine could do this?

I just went through the product’s FCC certification photos which gives you nice pictures of the product internals.

AFAICT, there were no readily obvious DP sensors to be found.