It's not just 1815, though perhaps that year has more complicated political and personal agenda than others. wherever you look at primary sources you can find contradictions, sometimes even in straightforward and authentic letters. Often there is no rational explanation.
As regards to the why Grouchy got his baton before d'Erlon, it would have been because Grouchy had already been given it in 1815, d'Erlon was a new promotion. I don't know whether anyone held any grudges against Grouchy by 1830. The quote you give just refers to a misunderstanding not to treachery, cowardice or incompetence.