Philosophía
"The devil made me do it"
huh? i'm not the one who stated unequivocally that superman holds back against cm. i was curious if that was explicitly stated somewhere given the way he declared it as an apparent fact. and if it is true (and i have no doubt it is given they are both heroes....) i equally have no doubt at all that for the same reasons, cm holds back against superman in their fights making it a wash anyway. /shrug
This question is easy to answer and it is done so in two fold, because it takes an understanding of Superman's holding back.
1). The conscious holding back. Superman has only not held back against Doomsday [DoS] prior to OWAW
https://imgur.com/a/NGYvjEi
Superman instinctively pulls his punches, even in the most extreme situations. He has done so even against omnipotent Emperor Joker:
https://i.imgur.com/F9HucG7.jpg
It's the reason Supergirl looked more powerful at first, for example:
https://i.imgur.com/6W5evTM.jpg
2). The unconscious power reserves:
https://imgur.com/a/1xGQzmj
Superman's power in its actual raw sense is literally dependent on the state of his mind. He can even depower himself, as he has done post-Infinite Crisis, as it has been made clear time and time again. Like here:
https://imgur.com/a/DORhNLX
He has to have a specific mindset in order to access his power. By altering his mindset, his power surges and he accesses more of it:
https://i.imgur.com/XHMjDYR.jpg
This same surfer of hidden power [which Loeb is playing off there] was what happened in DoS, at the end when he killed Doomsday on his deathbed:
http://i738.photobucket.com/albums/xx28/PhilosophiaKMC/RogerSternNovelisation.jpg
On top of this, he actually gets more powerful in critical situations and absorbs more solar radiation:
https://imgur.com/AHwLy5C?fbclid=IwAR29BajZpqoQl6Uy-kE5VKUZ4CLa1minMfSd0DVLJpLu8sBwDaOFE4rPwWk
So, in essence, you have 3 levels:
1). Holding back consciously [i.e. pulling his punches]. Superman does it extremely so but, obviously, Captain Marvel does it, too.
2). Subconsciously holding back. Even if he is not holding back consciously, he subconsciously is not accessing his power.
3). Amping himself by also absorbing extra sunlight in emotional duress.
---
To give you an illustration of the levels we're talking about here, here is pre-OWAW Superman stalemating Captain Marvel [who was accessing both Hercules' strength and Atlas [who is normally for stamina] while the latter is clearly trying his hardest to beat him, as Supes is like "wtf?":
https://i.imgur.com/dnpENog.jpg
Here is Superman training with Mongul to access more of his power [from the previous stalemating Captain Marvel w/Hercules+Atlas levels]:
https://i.imgur.com/XHMjDYR.jpg
Here is Superman, after that training with Mongul, double-teaming an Imperiex Probe, and they barely take it to it:
https://imgur.com/a/eoYXZx6
Here is the [conscious] all-out non-holding back Superman against that same Imperiex Probe by his lonesome:
https://imgur.com/a/B7CGolH
Here is the [conscious + unconscious] all-out Superman against an army of probes and he goes through them like butter for days:
https://imgur.com/a/V55CDhg
Levels.