No. It would only be fraud if they knew the methodology was likely to be extremely flawed and there are receipts with executives saying “let’s choose this because of X nefarious reason.”

Twitter being wrong about the number, or using a methodology Elon doesn’t like, isn’t enough.

The contract explicitly states the number could be much higher than their estimate, so although IANAL, I doubt it.

Fraud isn't about the contract, it's about if someone lies to obtain money. Saying the stats are x when they're y because x sounds better seems like standard fraud to me.