With this, we do not know if it is intentionally done by the MC, or if it's just something that comes naturally to him.
It may not be surreptitiously chosen by him, perhaps it's just autonomic?
We also do not know what his current upper limit is.
He saved Luna & beat the quasi-Capo, all while appearing totally out of his depth & bewildered.
The Contracts also add to his accomplishments.
He outsmarted the Nuns. He took total charge of the Snooping Bonans, with Leilanna (can't remember her rank, is she Elite?).
I wonder if/when the MC will face a challenge he cannot (yet) overcome...
Perhaps Dominico can give him the Hero's Journey failure, before the Frenetico, then MC faces him in the tournament, expected to lose again, but pulls off the win using knowledge learned in the defeat?
Well, at the moment, he feels content with where he is at, being at Soldato and not wanting to advance.
He's never felted the need (or desire) to become stronger yet.
When he, along with his rival get their training from the 4 Serpents some time later in the story, I think would be the time where he realizes before then that just his "survival mode" and "doing barely enough" to beat the opponents is no longer enough.
I mean it could happen when MC comes up against a much higher ranked member of an opposing Family. But it would be really interesting for me if MC does take a loss against Dominico in a practice match that really gets heated (and ends with Dominico pulling an unexpected move that MC didn't expect at all).
And like you said in Frenetico, MC gets serious and goes all out (no holding back) with Dominico in their spectacular bout that is close and with MC winning in the end (with loud applause from many in the stands, if there are any in the stadium. I'm guessing there are lol. And MC and Dominico's bout is talked about for a long time even after the Tournament is over).
Seen some say before that they think (and wish) MC is gonna last a long time in this world just using his "survival mode" and "doing just enough" attributes, but I disagree, and personally am not a fan of that route in terms of story.
One can only go so far without improvement, and if MC continues rising in ranks more and more without showing his limit and getting some training, sooner or later plausibility of it all drops significantly.