This happens in pretty much every Electron app as far I know, and lots of Electron apps are like Spotify, VSCode or Slack are very likely to be in the Top 10 or at least Top 100 most used apps. And yes, I would expect Apple to test at least the most popular apps before releasing a new version of their OS.
> Maybe the thought is that an email from Apple to the dev saying fix your code would more compelling???
Of course not. Apple controls the SDK, they could workaround this in many different ways, for example instead of changing how this function was implemented they could introduce a new method (they're both private so it doesn't matter) and effectively ignore the old method (maybe also they could add a message for developers building their application that this method was removed). It would draw ugly borders in the affected apps but it wouldn't cause this issue at least.