I've heard others say no, they don't drop out before, but I haven't yet
found one myself that didn't, nor anyone whose story about same seemed
believable. From what I've seen of GFI designs on the 'net, they operate
on
a "latch" system and that "latch" drops when the ac goes away.

I would like to see a URL to that design.

The designs I have seen "on the net" and my own experience are that the GFCI
contacts stay closed when the input power goes away.

You always
have to press the button to let power thru a GFI when they're new also,
according to those, so that seems to support my own experience. It might
have been wikipedia; not sure.

It definitely would be a good idea to "ship" with the device already
tripped. They will not reset without power being present. If it is wired
backwards (load and line switched) and pre-tripped, it will never pass
current (which is good.)