In the roblox community most unintended game features are often counted as "bugs" or "glitches", "Exploits" or "Exploiting" is often refered to the use of a 3rd party application that alters the game (Basically cheating like btools, extra speed, autoclickers etc)
A glitch/bug is a malfunction of the games code. A exploit/cheat/hack is a modification of the games code.
There is a clear difference. The sideways speed trick is a malfunction of the games code; therefore, it's a glitch or a bug.
Henlo this is your local FE2 speedrunning mod Nolyswag and I'd just like to recommend for people to use velocity display during runs to maximize the odds of your run being verified (it just helps confirm that your run is legit).
Signing out, Nolyswagger the 1st
