If it was an exploit don't you thing the dev's would have changed it? The fots on gates has been going on forever, I don't think it's an exploit at all. Like someone said its a tool to fight with, next you'll say using flame towers on gates is an exploit.
If it is an exploit you can bet dollars to donuts that no, they developers would not have changed it or fixed it, even having complete knowledge it is being exploited. There are literally enough exploits, bugs, and problems in this game to fill the Mariana Trench... and
maybe a hand full get addressed per year.
An exploit, in video games, is the use of a bug or design flaw including glitches, rates, hit boxes, or speed, etc. by a player to their advantage in a manner not intended by the game's designers. (google search the definition of exploit.)
FOTs are not designed to burn gates.
Breaking this down... applying this and a little common sense we get "Use of a bug or design flaw by a player to their advantage in a manner not intended by the game's designers."