That said, there's risk in globally deploying platform-level technology changes which could be difficult to roll back and are not held democratically accountable.
It may be worth considering time-limits on rapidly-introduced technology changes like this. We cannot always anticipate all the side-effects of technology, and if we do need to introduce them suddenly, we should be thoughtful and deliberate about evaluating their effect as we do.
It seems apparent that Apple and Google are the entities holding the reins on this particular implementation. Yes the technology is opt-in; but that could be seen as a way to make a potentially bitter pill palatable for both citizens and their governments.
After a global recovery, imagine what the world might be like if nearly all daily interactions between people with Android or Apple smart devices have to be assumed known to their local authorities (including in locations with repressive regimes).
Perhaps that would appear acceptable, under some circumstances, to some people in some cultures. I think it'd be hard for almost anyone to quantify.
I'd suspect that an environment like this would lead to a significant loss of privacy and a resulting chilling effect in the types of activities and relationships that people build.
Even if that's a pessimistic outlook, it may be worth questioning whether two corporations from a single country should have the power to effect such large changes without at least constraining their effect to the duration of the COVID-19 crisis.