But do we agree that not all devices can?

By not all you mean motors with windings connected to grid? Well, they still will work on higher frequencies, but on higher speed. Real problem is low frequency, not high. Well, 0.5kHz not all devices can handle, but most consumers(even conumer electronics, no pun intended) even rated to 50-60Hz range. So 46-64Hz should be fine for them.

What about sensitive devices keeping patients alive in hospitals?

Sensetive devices that can't handle range bigger than ±0.4Hz? Are you kiddding me? How does that even pass certification?

Most frequency-sencetive devices are not consumers, but transformers and turbines.