Hmm. When I became a Canadian citizen, the interview officer had a detailed list of all my entries into Canada as a PR (using my visa-exempt foreign passports). So that suggests that the "link" you refer to already exists and could be used to determine if residency requirements for PR renewal had been met or not.

And it still does not explain why "hitting" Canadian citizens is part of the intented effect of an eTA. Once you're a citizen, no more requirements to be "gamed".