Defending the Dallas 11 personnel with Cooper, Lamb and Gallup is a lot different than defending it with Cooper, Lamb and just some guy.
Having 3 very legit WR’s is going to create enormous headaches for defensive coordinators. Out of the gate this season, defenses will have to determine if they want their 3rd/4th corner on Gallup or Lamb. Either way it is likely going to create huge problems for them because Gallup (who probably is the least talented of the three) is still a really good receiver and can absolutely light up a 3rd cornerback.
However, if the defensive coordinator decides to cover Gallup with their CB2 and let their CB3 handle the rookie... that is going to be a recipe for disaster because Lamb is going to catch a lot of balls if he isn’t handled by a very competent DB. A lot. And once Lamb is into the secondary with the ball in his hands, all bets are off because that dude is going to eat you alive with RAC.
And all of that is with the understanding that Cooper is going to be getting his catches. Decide to single cover him and move a DB over Lamb or Gallup and Amari will probably go off, unless your CB1 is a true stud.
Coordinators will probably try putting putting their CB1 on Cooper, their CB2 on Lamb and maybe their CB3 and CB4 (or safety) on Gallup to try to limit the damage those 3 guys can do. At least that’s what I’d probably start out trying to do.
The problem with that is... well... Ezekiel Elliott.
Zeke and his line usually play well against small defenses like the ones that will be necessary to mitigate the damage that Cooper/Gallup/Lamb can do. Love Elliott or hate him... one thing we can all agree on is that he is a load to bring down and if he starts breaking into the secondary and bludgeoning the DB’s that are having to deal with that loaded WR corps., it is indeed going to be a long day for that defense.
If they don’t go small... the Dallas receivers are going to have a day.
It will be simply a huge, huge problem for coordinators to figure out.
By taking Gallup away and putting in someone like Wilson, you make things easier for the DC by a good bit. There are CB2 and some CB3 that can cover Wilson and remove him as a weapon. Heck there might be some LB’s that could take him out. Then, they could concentrate on Lamb/Cooper and try to limit them. That would likely be doable with 1 less DB than if Gallup was in there.
It might not seem that different but it is almost like giving the defense another guy to play with against the run. The problems would be far greater with a dangerous WR in there like Gallup instead of some WR that doesn’t really scare defenses.
That’s a simplified example, but you get the idea. Having a good WR in as your third option changes the way defenses will attack your offense.
Gallup is very good, he’s cheap, he’s a good locker room guy, and he has a chance to become a very, very good player. Not to mention that not having Gallup would much more pigeon hole the Cowboys into having to keep Cooper beyond 2022. It would be lunacy to get rid of that before the 2020 season when you’d simply get a 2nd round pick in 2021. There’s really no good reason for it... and plenty of reasons not to do it.
just my $0.02