It is true that this will address the issue, however it's generally better to use a specialized tool to swage the metal back into place rather than simply filing it away.If dry firing on an empty chamber isn't a regular thing, any damage to the opening to the chamber can usually be dressed with a small round file.
It is true that modern rimfires are generally more likely to be safe to dryfire than vintage models, however it is not true that all modern rimfires are safe to dryfire.All modern rimfires that I know of can be safely dry fired.
It's best to consult the owner's manual or the manufacturer before dryfiring ANY rimfire, modern or not.
That's essentially saying that a rimfire designed to be safe to dryfire is safe to dryfire.Rim fired guns with properly fitted firing pin, without excessive absolute protrusion, are safe to dry fire.
If the firing pin doesn't protrude far enough to reach the breechface then dryfiring it won't damage the breechface. If it does protrude far enough to reach the breechface (and many of them do by design) then it will damage the breechface.
Your assertion implies that any rimfire with a firing pin that protrudes sufficiently to reach the breechface does not have a "properly fitted firing pin". I suppose that, in one sense, there's merit to that view, however, in reality it doesn't change anything from a practical standpoint.
Some rimfires are safe to dryfire, some are not. The best way to figure out which is which is to contact the manufacturer or read the owner's manual.