Leaderboard

My best recommendation is to just not use the same PID and set of information for an assortment of different Pokemon in the first place. Depending on how XD generates its Pokemon, it may just be impossible for the game's Hitmonlee to have that specific PID while other Pokemon can have it due to their specific circumstances. Specific combinations of IVs, nature, species, and gender (if applicable) may simply not work, depending on how the RNG in XD is rigged up. Hypothetically, it should work as long as you're keeping everything completely accurate (met level, encounter location, etc). But gen 3 RNG + PID creation can be a bit whacky at times... and copy-pasting PID across different species is already getting into messy territory with editing. I cannot name your exact problem here, but it shouldn't surprise that some of your results are flagged as illegal when you're making edits that range into the very implausible (multiple different Pokemon having the same PID).

The fact is that in XD not every PID is actually reachable: some are skipped because of the non-shadow pokemon generated before the shadow one. As for Rhydon, there's not a non-shadow pokemon generated before it, so, in theory, any PID should be valid. With XD, however, Pkhex is still quite inaccurate, since it flags illegal pokemon that are actually legal, and vice-versa. In the end, my recommendation is: if you want shadow pokemon to be legal, you have to actually catch them and keep them as they are.