yes... The score doesn't state what that ambition is aimed at...
In this case it's pretty clear: the lad is your typical Musclehead whose only goal is to become the very best in.... in this case looks like any infantry weapon he decides to pick up.
To the point where he drops any and all allegiances if it means he can Train to get Better.
That may be a problem in the future, but right now it gives the mangaka an excuse to draw yet another Ars-Face..
Note how at the start of the siege it showed other soldiers being afraid of or look down on him.
Monkeboi had no loyalty to that side to begin with, so he didn't care about betraying them (his initial resistance can be put down as him not wanting to lose/surrender without getting to fight, because ook ook)
Now that he's developed a self-made worship to Ritsu, it's unlikely someone else can repeat the same.
If similar situation happens soon, then monkeboi would think he hasn't studied under his master properly yet and thus wouldn't switch.
If it happens later, well, Ritsu would've clearly beat the mistakes out of him so there wouldn't be any for someone else to point out.
And obviously Ars will reward him properly even if he's commoner (see: the rest of Ars vassals) meaning there's also very little odd of some lords pulling him away by making 'better' offer.