The PR spin is very interesting. In reality, if the team are extending, they only want a short term deal. No team will take the risk of being tied to a long term deal with a QB who has shortcomings.
On the flip side, any agent would advise a client like Dak to take the longest, most guaranteed contract. You want the team to be forced to keep you for several years and maximise your guaranteed income in case you're not really elite. If there was a 5-7 year deal on the table, Dak's agent would be advising him to sign asap.
Dak's team know the Cowboys have reservations about him - this is why he hasnt already been extended. They know they will not get a 5-7 year offer. Their realistic best case scenario is a 2-3 year deal. So the PR spin is that Dak only wants a short term deal.