Both the team and the player know that a seven-year deal isn't a seven-year deal. It's a three- or four-year deal that the player lets be longer because it gives the team flexibility for spreading out bonuses and restructuring purposes.
This is only Martin's third year to count more than $10 million against the cap since signing his deal. His deal was very team friendly. Compare it to the four-year deal that Prescott signed. He has counted at least $17 million each year of the deal because the team had nowhere to push the money. It put two void years on the end just to be able to spread out some of the hit, but, of course, having just void years mean the Cowboys have to do something with his contract next year because they can't restructure it anymore. Most likely that means an extension since he is set to cost $59 million against the cap.
Martin could have been like Dak and only accepted a four-year deal with void years. Then the team would have been forced to redo his deal this year instead of Martin trying to force them to do what's right.