Anyway, we've never before seen the 2230s depicted onscreen, so why couldn't they have used different conventions in that generation than in later ones?
Especially since a leading 0 had been used in Enterprise (recall, it was the NX-01, not the NX-1). I understand that Enterprise was the first time we saw such low numbers, but the fact remains: they, too, could have chosen not to use a leading number. Though there was no convention saying one way or another, perhaps making the Kelvin have a leading 0 was an intentional homage (unlikely, but perhaps) to the concept of leading 0s seen during the 22nd Century.