I found that conversation on the other forum a little hard to follow. What I know is from how I got my shiny manaphy. On the original game that received the egg, the manaphy does not hatch shiny. I RNGed it using a spread that is shiny on a second game. So before the egg hatched, I cloned it and I traded it to the second game and hatched it there. Hatched on the second game, it has linked trade in it's description. Hatched on the original game that received it, it's a got the Pokemon Ranger info, whatever that is. I'm not looking at the poke right now.
Anyhow, Game Freak didn't want it shiny ever, so there's some sort of code check that is active on the game that receives the egg, but that same code fails on the second game you trade the egg to. So that's why all shiny manaphy must be hatched on a second game and therefore have linked trade in the description.