I'm well aware he helped write riffs for the first two albums while he was still with them. That still doesn't mean that Hanger 18 doesn't have similarities to The Call of Ktulu that was wrote 6 years earlier. There's even Youtube videos on it.
And I'm not sure how Orion can be a version of a song that was wrote four years later. Not that I hear a similarity between the two anyway.
This was one of my favourite bands before they broke up. For a band that was labelled "screamo" and put on very loud shows, they had a group of musicians who were quite talented. This entire LP was different from their normal stuff, but this song was completely off the wall for them.
He wrote the Dminor riffs though, and it's not that they have similarities. They are the exact same with identical notes, but Ktulu is way easier to play. Orion a version of what? It doesn't resemble anything from Megadeth as far as I know.