The kids that were roughly the age of Boba (and played by that actor) in Attack of the Clones wouldn’t be fully aged up to the same age as the first batch of Clones from that film by the end, or would be barely of age. The clones age roughly two years per year (excepting Boba), so if that batch were 10 when the Clone Wars started, they would maybe be 20 by the end (relatively).
We also see a batch that is relatively the same age as Boba (half his age objectively) in a Clone Wars arc that would not have been that long before the end of the war (five years is an incredibly short period of time anyway).
I also don’t think the Kaminoans knew the Clone Wars were ending when they did, and as a business would likely have liked to continue supplying the military force (as we see with their senator in The Clone Wars), so it makes sense that there would be more young clones.
All good points. Thanks for clearing that up, I couldn’t be bothered doing the maths myself! 😃