I think it's pretty clear what I'm asking.
It is not a norm in other companies to penalize people's performance reviews for failing to complete routine training. What is a norm is that your manager at some point simply demands that you stop what you're doing and complete the training. What would happen if you refused? Who knows? I assume you'd get fired for cause, the same way you would if you deliberately disregarded any other directive. Like I said: the most sophisticated training programs I've seen simply cut off people's access until they complete training (and thus, obviously, if you refused to complete the training, you'd be let go.)
The Perf downgrade is high-drama. For one thing: it sets a dollar price you can pay to not comply! For another, it throws the objectivity of performance reviews in question (there are multiple factors that affect your Perf level, not just this one!).
So, obviously, my question is: why does Google have this weird, elaborate, high-drama mechanism when it could instead just do what everyone else does: the CEO tells the VPs that all their reports need to complete training. The VPs make it happen, or are replaced. Recurse.