I just checked what was my first shiny which was my Numel and it's showing up as "possible method J/K slots don't match encounter".
I chained it near Stark Mountain on my Diamond game and transferred it a long time ago. I just never bothered to check it.
https://www.pokecheck.org/?pk=5449549
Edit: actually I'm not positive it was chained as it was a long time ago but there was no cheating involved.