I work in banking so let me give me two cents (I may be late but I'm too lazy to read the rest of the thread):
What you posted isn't out of the ordinary at all. Most celebrities, athletes, people of high net worth don't have their money in personal accounts. Most create corporations/LLC's and have direct deposits to fund their personal accounts which also helps them not spend as much (ideally). It'd be very unsurprising if Ohtani didn't have some type of LLC set up with a few "signers" on it who can essentially do anything on an account with the exception of close it, open another inside of the entity, or add more signers. I'd assume in this case Ohtani's lawyer, financial advisor, and (apparently) his translator were signers, and therefore Ippei could've easily sent a 4.5M wire on his own
My assumption is what's already been posted: Ohtani signed off on the wire or gave the approval for Ippei to send it and then retracted his statement when he realized there are laws against wiring money for illegal gambling
FWIW, anything over 10k is reported, yes, but wires don't fall in that category. It's only if it's physical cash being withdrawn or deposited from an account. Even a $20k check/cashiers check/20 money orders totaling $20k ($1k max per money money is the rule) isn't reported unless the person getting the cashiers check/MO is giving paper cash in exchange
Keep in mind in business accounts it's a lot more laid back. In a personal account I can't go to a bank and deposited paper cash into your account unless I'm on the account as an owner. It would have to be a check/MO/cashiers check. In a business though, anyone can deposit cash into an account.
The only thing that prompts the report is over $10k of cash in a single day. If I went to a Bank of America now and took out $6k and then another branch tonight and did it again, that is reported, but if I wait for tomorrow for the other $6k, I'm good. Of course doing $9k one day and $8k the next and $9500 the next day is called layering/structing and is just as bad, but again, a wire for 4.5M is not reported