The rules say a player "knocked over" for any reason must make an armor roll. Everywhere else that an armor roll is mentioned the words "knocked over" are used except for GFI and Leap.
GFI used the words "trips up and falls prone." (i.e. nothing knocked them over) There is no mention of an armor rolls.
Leap which I see as very similar uses the words "fall over" but then specifically mentions that an armor roll should be made.
Initially I used to play where GFI did not cause an armor roll but was convinced by others that it should. Now I can't remember why I was convinced.

Someone convince me again.