It's not deceptive at all. It's very clear in what it tells. The Cowboys DO NOT SPEND AS MUCH CASH on their roster as most other NFL teams. You are falling for the trick the Cowboys are playing. Cry poor. Cry dead cap. Cry no cap space.
Cowboys operate under the same rules as everyone else and somehow, someway, a 90% of the other NFL teams have found ways to spend way more cash on their roster than the Cowboys and do so while still staying under the cap.
There's no correlation that signing your guys somehow results in more dead money/mortgaged future. Dead money is dead money whether it comes from your guy or a FA you signed that you eventually cut. The Cowboys simply don't manipulate the cap the way other teams do and as a result, they don't spend cash like most other teams do.