But, whether using a ff lens or not... there’s still a crop. My understanding is that an EFs lens with 50mm printed on it is 50mm IF that lens is not cropped by the sensor. The FOV is actually 50mm x 1.6 = 80mm on a crop sensor. So, in my opinion, the FF lens vs crop is moot for getting the wide shot. The sensor will crop the FF image circle, so one is cropped either way. I guess what I am not seeing is how in the world choosing an efs lens helps in any possible way. I don’t believe it will make the shot wider.
So, usually you cant put an apsc lens on a ff camera because the image circle isnt big enough.
But if the sensor is cropped to use the same size as an apsc sensor then it will work.
A 50mm FF lens on an apsc sensor would be cropped by 1.6, so you end up with a 85ish mm equivalent.
A 50mm efs lens on an apsc sensor should have the same focal length has a 50mm lens on a FF sensor.
Where you'll find the difference is in the way the aperture works. Afaik, f2.8 on FF isnt equivalent to f2.8 on apsc, it still applies a crop to that. So to get the f2.8 FF equivalent on the apsc sensor, youd need a lense 1.6 times faster.
So that same EF 50mm f2.8 would be both longer and slower on an apsc sensor (roughly 85mm f3.something). This wouldnt apply to efs lenses on the apsc sensor because you're not losing any of their image circle.
Long story short, I think having the option would be good