It depends on whether the issue is that iOS is terminating background apps before they’re able to flush to disk or whether the issue is that the app isn’t flush

It depends on whether the issue is that iOS is terminating background apps before they’re able to flush to disk or whether the issue is that the app isn’t flushing to disk when sent to the background. If the former that is Apple’s problem to fix. If the later they are absolutely right to point the blame where it belongs, on the developers who didn’t code to the platform standards. If it is the later, those same apps would have lost data under iOS 12, and they were just lucky that the termination algorithms were less aggressive.