And Righteous Might is a standard cleric spell, so any cleric (regardless of domains) can cast it, so it doesn't really tell us anything we didn't already know (namely, that Durkon and not-Durkon are both clerics).

Thor's Lightning is probably also a renaming of some other spell, but we don't know which one, and none of the likely prospects is on the standard cleric list, so we continue to list that one explicitly as something that Durkon has, and which presumably came from one of his domains.