There's a reason why they call these normally impossible runs "TAS". Tool Assisted Speedruns utilize a tool or an exploit in the engine to make shortcuts in the game and thus make these quick playthroughs. If it's done only with glitches though, then they can still be considered legit, especially considering that glitches in the original 64 game have been made into features in the 3DS remake. See also "Sequence Breaking".
In short, can Legend of Zelda: Ocarina of Time be beat in 8 minutes? Normally, no. However because of the glitch being used to get there, it is possible.