>>4399429The focal length isn't any different, what's different is how large of a sensor it can cover
There are plenty of "designed for smaller sensor" lenses that cover larger sensors, and you'll notice the focal length isn't any different than what's labeled
Any 20mm you put on a crop sensor camera will be "cropped in" compared to a 20mm on a FF camera, since all the "crop" stuff is a camera thing, not lens
Any 20mm you put on a crop sensor camera will look like any other 20mm you put on it (in terms of field of view), regardless if the lens is meant for FF or crop
