It would be a configuration nightmare is every time a change was done on an oil filter model that the p/n changed. People couldn't even keep up, let alone the application data base for all the vehicles in the world. In a consumer product like an oil filter, if it still works on a engine it's specified for, they could keep the model number the same forever. I believe Motorcraft does indeed change the actual Ford p/n on some filters when they change design, but the model number would remain the same.
Fram did make changes to some filters that basically had a recall on them (long time ago) to improve them, and added and "A" at the end of the model number. Mobil added an "A" to the end of some model numbers when they changed. So some makers do try to designate a change when it's warranted. But in general, configuration control is up to the company designing/making them. The configuration control I was doing was specified by the military, so it was nitty-gritty almost to the point where if you changed the color of something i rolled the dash number on the part number. It could get nuts at times.
