Please reread the article. I am using deferred just as intended according to the Google guy in your linked issue: “Deferred FKs is for validation”. The whole article is about working around this “brief moment between replace and delete [where] our foreign key constraint in the Car instances which refer to the to be updated Color is violated” when not using deferred.

And yes, this is working perfectly fine in live apps for hundreds of thousands of users. ;)