Although Nintendo did not make shiny checks in gen 3, the only possible way one has obtained the shiny Wishmkr Jirachi is if someone backs up a Gamecube sav and change the seed to one of the shiny seeds.
If you believe that externally editing the save file in order to force the game to generate a shiny is legal, fine. These Shiny Jirachi are semi-legit at best as the shiny Jirachi were not naturally obtained. Unlike RNG abuse, these required the use of external devices. I beleive he did this experiment several weeks after the post in red; I don't know his final conclusion (why didn't he edit?). Shiny Jirachi are there; Kaphotics's bundle were probably obtained through the edited seed.
On another note, the 9 possible possible IV/PID combinations for a shiny Jirachi are known; therefore, anyone with the knowledge can create one in Pokesav and satisfy legal.exe.