Majora's mask is an n64 game but the fastest version is Wii Virtual Console so all runs are done on that.
Dolphin is an extremely accurate emulator of WiiVC but has the slight issue that the reset skips much of the classic controller text and spinning n64 logo etc. 
These things combined with the fact that Dolphin emulates VC perfectly would make dolphin by default the fastest version, something which we obviously don't want happening.
The n64 emulators are allowed as these are riddled with problems that would never allow them to be competitive.

Hope that clears it up.
TL:DR Dolphin is quick af.

The Legend of Zelda: Majora's Mask

dolphin as an emulator?

Grand Theft Auto: Vice City

Mario Kart Wii

Pokémon Red/Blue

Pokémon Snap

Wii Sports Resort

Minecraft: Java Edition

The Legend of Zelda: Ocarina of Time

Minesweeper

The Legend of Zelda: Majora's Mask 3D

Ocarina of Time Category Extensions

eastjesusnowhere