They've got a power and force that you've never seen before

[Wisemon]

but Alpha warned him that the Power Coins' destruction

Right, just like I said. Alpha warned him that because the power coins were destroyed, morphing was risky.

equally charred Mastodon Power Coin in it

This is where I disagree. I didn't see a charred coin. I saw an empty imprint. This would correlate with the theory that they're all the same coins, because the coins weren't charred, they were crushed to little gold bits. If they weren't the same coins, then it's possible that Goldar and Rito only destroyed the Ninja coins, but that would leave a much larger plot hole. If there were still another set of dino coins, why didn't they figure out a way to recharge them instead of relying on the Alien Rangers and the Zeo crystals? Also, how did the coins get "charred"? My explanation won't leave you tearing your hair out.