I'm not sure if it is fraud or not. Maybe an attorney can comment, but here is how I look at it:
Fraud:
(1) a false statement of a material fact,
(2) knowledge on the part of the defendant that the statement is untrue,
(3) intent on the part of the defendant to deceive the alleged victim,
(4) justifiable reliance by the alleged victim on the statement, and
(5) injury to the alleged victim as a result.
The attempt at buying coins on coinbase while selling coins outside of coinbase, then if the coin price falls… If Coinbase doesn’t deliver the coins according to their TOS and you say to the bank that you want to do an ACH chargeback due to them not delivering, it doesn’t fit the definition of fraud in multiple ways:
The statement you would make to the bank would be: “Coinbase did not deliver the coins based on their TOS so I request my money to be sent back to me via ACH chargeback and if they do send the coins, I will send them back to Coinbase”
1) it isn’t a false statement
2) doesn’t apply since it isn’t a false statement
3) not deceiving anyone
4) they are relying on it, but it isn’t false
5) no one is injured since Coinbase waited to fulfill the transaction, they can just resell the coins at the current market price, assuming they are able to actually sell coins.