I thought he was waaay overrated coming out (pretty sure I even created a thread about in the draft forum that year) and overdrafted by the 49ers.
He was a guy without a true position and tweener in terms of physical size (6’-2” 273 lbs). When you watched him at Stanford you saw him make plays but you also saw him getting completely washed-out and rag-dolled, especially when he took snaps inside.
I think he’s best suited as a designated rotational pressure player on the inside. He doesn’t have the repertoire to man a starting spot outside nor does he have the size to be a 3-down tackle inside.
With all that said, it may sound like I don’t like him but that wouldn’t be the case. The 49ers made the mistake. I think he has some utility and it’s just a hunch, but I wouldn’t be surprised if based on their supposed infatuation with Ed Oliver that the Cowboys see a similarly sized/skilled and cheaper alternative in Thomas.