That is exactly what I was wondering. Barrs stock supposedly took a hit after the combine and Mack's improved/stayed the same. I thought Mack looked good and in games he did everything successfully. He would be an incredible weapon for Williams. He has been compared to Ricky Jackson. He is a very strong pass rusher and plays the run well. He may not be good at dropping deep, but he covered well near the line.
That being said, he is a luxury for the Rams at this point IMO. They have more important needs.
They both came out pretty unscathed, to highly praised, I was just giving my point of view. Once these guys talk a guy up so much, it's hard to back out. I don't have a dog in the fight, nor did I watch a ton of film on Mack. Again, just relaying what I saw out of him, and I was rather surprised, which is why I made a note out of it.
Stiffness in a LB isn't always a bad thing, and it doesn't always translate, see Trumaine Johnson as a corner--he does fine with the stiffness he has. Jarvis Jones had a terrible combine, yet they talked him up last year, even as he totally struggled in the drills.