That is, by definition, breaking backwards compatibility. I.e., the code that I wrote against version X will not run against version X + n. They just give a war

That is, by definition, breaking backwards compatibility. I.e., the code that I wrote against version X will not run against version X + n. They just give a warning about it in version X + (n - 1). Backwards compatibility means that my code will run against X + n for all values of n >= 0 without modifications.