... the radial tires can cause more flexing, sometimes resulting in full wheel covers coming off.
As noted in the SEMA article above, radial tires do change/concentrate the loaded area of the wheels which could be a problem. Image # 1
Cracks around the lip of the wheel mentioned in the article don't seem to be a problem on stock 50's Ford wheels, given the lack of its discussion among 50's Ford owners and the very common use of radial tires.
Wheel covers coming off happens fairly often, but isn't limited to 50's wheels.
It might be due to a combination of things. A bit of wheel flex, aged wheel covers, etc.
The usual solution is to bend the wheel cover tabs farther outward for a tighter grip.
I've got a '57 that has newer oem style steel wheels with the safety beads (the original '57 and older wheels don't have that safety feature) and one of the front wheel covers still came off a couple times.
Because the wheels that came with the car don't fit as well as they could I got an original set of wheels, and another set of wheel covers in better condition. They aren't on the road yet.
(The wheel photos # 2 & 3 are just examples, not the actual wheels off of my '57.)