Ignoring all of the Dak-vs-Romo agendas, I think this is more than just about Dak playing well. The Cowboys rushed Romo back last year in an attempt to save the season and ended up losing him for the rest of the year. Given how serious of an injury Romo had in pre-season, the Cowboys are likely being very careful and patient with his recovery process and will bring him back slowly. Having the Cowboys sitting at 5-1 has made that decision even easier of course, but think about it from a strategic angle.
Ignore whether they plan to start Romo eventually or not as that does not even matter for now. Just think about it purely from a record standpoint. Let's say the target for Romo to be active (not saying start, just fully recovered and active) is the 9th game. The worst the Cowboys can be going into to that game would be 5-3 and the worst they could be out of first place is 1 game. Again, that's the two worst case scenarios. At that point, the season and first place in the NFC East would still be within the control of the Cowboys as they would still have another game against the Eagles and if they beat the Giants and Commanders in the second games as well, they would likely end up in first or tied for first at worst.
So at this point, there is no reason to rush Romo back (no pun intended). If the Cowboys beat the Eagles and/or Browns, that just adds more time the team can give Romo before he returns to active status on game days.