Has this (a) been exploited in the wild, and more importantly, (b) even actually patched in more recent phones?

Otherwise, how is this a justification for upgrading your phone? It seems like you may have forgotten what the argument even was. I was arguing against routine 1-2-year upgrades, not against the entire concept of upgrading for something wiht a serious security vulnerability. If a serious exploit appears in the wild and your only solution is to upgrade -- by all means, go for it. But is that the case here? And this happened periodically every 1-2 years for you to justify upgrading equally often?

A) I don't know. How would you ever know? RCE can be silent.

B) Yes, in Android patch level July 2017 and iOS 10.3.3.