Having run a business, 6 figure amounts are routinely moved via ACH. Some banks make it hard for consumers to send money to a random person’s account via ACH, but within the US, it is always possible and is literally how most companies pay their employees.

It was a bug in my use case but now I understand.

How does a wire transfer “put the risk on the banks”?

With a wire transfer, the sending bank earmarks funds and moves it to a special account. Once the central bank confirms, the destination bank takes money out of their account (this is where the delay occurs, as sometimes the bank must setup a repo with the central bank) and sends it to the recipient. If the sending bank where to fail, the recipient still has their money. Now its up to the sending, central, and destination banks to duke it out for the money.

I am referring to US wires in this case

A "wire transfer" is the thing you pay $40 for, and is immediate and irreversible. Individuals probably only ever use it when buying a house. (Within the UK, this is called a CHAPS payment.)