#4 Losing against MJF would drastically diminish CM Punk's star power
CM Punk has been in the wrestling industry for decades. The extensive career he has had so far has garnered widespread acclaim in the wrestling community, along with earning him a cult fan following. No one can deny his hand in legitimizing AEW as a serious contender against WWE.
On the other end of the spectrum, MJF is a homegrown AEW star. The young wrestler has proven himself to have incredible potential on the mic, bringing a despicable heel to life on screen. Furthermore, his in-ring skills are also not to be ignored, as seen in his fight against Darby Allin.
Even on objective comparison, CM Punk is definitely the star with a bigger following. The star power that Punk brings to the table is simply legendary. Conclusively, a loss against MJF would affect that star power drastically.
Tony Khan would obviously like to do what's best for business, and taking down Punk's star power just to build MJF seems unlikely. This might play a major role in the match between the two, and tip the scales in favor of the veteran.
#3 MJF might not be staying in AEW permanently, unlike CM Punk
It is no secret that MJF has dropped a lot of hints about leaving AEW for greener pastures after his contract expires. While fans aren't sure if Maxwell is just playing his heel character or legitimately threatening to switch promotions, the fact remains that the Dynamite Diamond Ring winner could possibly join WWE in 2024.
CM Punk, on the other hand, has fractured relations with Vince McMahon's company. Considering the value of the Straight-Edge superstar, it is unlikely that Punk will be leaving AEW for any other promotion.
Following that logic, MJF gaining momentum by defeating Punk will not pay off for the promotion in the long run. It follows that the Second City Saint coming out on top in Chicago will probably be the more feasible option.