But I think there's a clear reason why they so blatantly spells out "time vortex" in the mid credits scene. If he could have just gone out with the regulator, then there would be no need to mention time vortex in that scene. And then that scene would have been for naught. They mention time vortex because that's the next step for Scott, and he wouldn't touch a time vortex if he could just grow out of the Quantum Realm.
All the time vortex talk somehow in my mind came off as a "when they need to undo the snap in avengers 4 Scott will suggest to use it to go back in time" rather than his ticket out of the quantum real.