Actually it is CheckFreePay, and it shows up so if the receiving bank would show the payment path. Not all receiving banks would show the payment path. AMEX for one, does not. There is no difference from when you push payment from your real bank to pay bills if your bank uses CheckFreePay system. As far as I know, BofA uses CheckFreePay, so as PNC and TD and many other banks for their Bill Pay service. You can see the interface of it, is identical on any bank that uses the service. My guess is, the set amount of WMBP could trip wire. Using a real debit card that has amount far exceeded the 2K limit probably would not cause anything.

Using too many payment accounts actually has greater risk. Some banks actually limit to only 3 Payment Accounts.