Mark Lloyd writes:

Why should switching power to a GFI trip it? A GFI works on difference
on current flowing in 2 parts of the circuit. Both are being started
and stopped at exactly the same time.

I have a portable GFI that's intended to be used with extension cords or
portable tools. It's in the form of a 15 A extension cord (male plug on
one end, female socket on the other) with a GFI in between. It drops
out any time the input power is lost. You have to "reset" it initially
whenever you plug it into a new power source.

I assume this is a safety feature - you don't really want a power tool
restarting on its own after it has stopped because the line power went
away. So some GFIs do drop out on power loss, just like a magnetic
starting switch for a large power tool.

On the other hand, the wall-outlet type of GFI does not trip on power
loss. It behaves more like a circuit breaker.

Dave