So, is the answer "Yes?" This technique would be a workaround to have more timely funds availability, i.e. to send from the account that I want to withdraw the funds from and into the account I want the funds to end up?

Otherwise, I'm confused as to the reason for the 3-day hold and how that gets around Reg. CC requirements. The CSR mentioned that NACHA rules allow for a 3-day period for the other bank to return the funds/cancel the transaction and that is the reason for the hold.

The three day hold is legit because the transaction isn't an ACH credit and therefore isn't subject to the regulation. On the flip side, if the transaction originated with Bank B and hit your account at Bank A as an ACH credit, Bank A would have to make the funds available the same day if received before 5 p.m. or the next day if received after 5.

Thank you for the explanation, by George I think I got it