The "sustainable" comment wasn't about the hosts file ballooning to the point of causing performance problems. It was more about the engineering effort required for every program ever (or at least every commercial program that might want this sort of analytic) to have to parse and edit a text file on both installation and removal, without messing that important text file up.

Do you really not see scripted editing of shared system-wide text files as a step back compared to the general containerization that app development has moved towards? This sort of approach would be explicitly incompatible with sandboxes. Adobe can only get away with it because they're already very entrenched with their own app store on their users' machines.