It's not solely about adding muscle.
It's about being able to use the muscle. I was a high school wrestling state champ back in high school at 157 lbs. I was around 6' tall then so obviously I was pretty skinny. Hardly ever lifted, about 200 lbs was the most I ever benched back then. Wrestled all kinds of guys that were shorter and stocky...some just with incredible builds. One was a state weightlifting champ.....he laughed at me at weighins. I had no trouble dealing with his strength advantage by using my length and leverage to counter it.
There are tons of kids I have wrestled with and helped coach that have that "country strong" feeling. It's hard to explain. If plain weightlifting strength was the determining factor for these guys, Costa probably should be the best OL we have. He is likely the strongest, but it is obvious that with all the strength he has, he doesn't use it well.
Arkin does seem improved...it wasn't that he would get pushed back a year ago, it's that he would get blown up. Not seeing that so far.