That man is Patrick Wildenborg, and he has revealed all in a new interview. The feature was chopped from the game's full release, but an intrepid modder - along with his friends - stumbled across traces of it within the game's PS2 source code, and eventually made a PC mod public.
GTA: San Andreas is notorious for many things for good or ill, but none so publicly scrutinised as its infamous 'Hot Coffee' mini-game.