PKHeX shiny question

[OdysseusOfGaming]

Ok so, I started an Emerald savefile the other day in order to get to the Battle Frontier, and so that I could get through the game quick to reach that point I generated a pokémon so I could just set it to level 100 and sweep the game in a couple of hours. For fun, I made it a Beldum.

And it came out shiny. I didn't click the shiny button or anything, it just automatically made the Beldum I generated shiny, with a legal PID.

So my question is, what are the odds of that? I dunno how this counts since it was generated on pkhex, but did I just accidentally create a legal, full-odds shiny Beldum encounter in gen 3?