It depends on how you define "understand". I think we all know what the CAP is. It is simple math. You have 53 guys and you have to pay them all and fit their contracts under the number the league sets as the CAP. Dallas does that every year just like every other team.
What the Cowboys do not seem to understand is what that means in terms of building a roster. The CAP is just a parameter. Even before the CAP I am sure teams had budgets for players. Rich teams could afford more for player contracts, poor teams less. But they all knew what they were working with. A CAP or a budget, forces teams to do a better job of evaluating talent then paying their talent closest to what they produce on the field. Getting under the CAP is easy. Getting the most talent out of that number is the hard part. Ideally, you want to underpay for talent. Worst case scenario is overpaying talent.
The Cowboys fail in this area. They overpay their own players. They did it with Romo. They did it with Zeke. They did it with Dak twice. I think they did it with CeeDee, and they will probably do it with Micah. I would argue they did it with DLaw and Zack Martin in a way. They did it with Terence Steele. Overpaying 1 player by a couple of million is not going to hurt that much but when you overpay 4 or 5 players it adds up.
Perhaps the Cowboys know this but realize they don't pay free agents so they can overpay their players not needing the CAP space to sign others. Perhaps. But it doesn't sound like it based on Jerry's recent comments about paying Dak $60 million. It sounds like thinks it was good to pay Dak $60 million even though no one thinks Dak is worth that kind of money.
I think what Howie Rosman does better than Dallas is he evaluations talent better and he figures out how to get the most talent under the CAP. It's smart. First look at the talent, then figure out a way to fit it under the CAP.