I completely agree with you and have been on the other side of this too, having worked on a native enterprise app running on various MacOS, Windows, iOS and And

I completely agree with you and have been on the other side of this too, having worked on a native enterprise app running on various MacOS, Windows, iOS and Android versions. Customers don't care if you have a great explanation why stuff with your app doesn't work. That being said, it's completely unreasonable to have the proactive expectation of something working well today (writing many files) breaking tomorrow (due to defender heuristics changing) and proactively trying to prevent this by optimizing. Mozilla reacting to this by both reporting the bug to Microsoft and optimizing to work around the problem is really the best you can do. "They shouldn't have written so many files in the first place" is not a valid preventative strategy, but a one way road to premature optimization hell.