Confirmed Address: What happens when account is not confirmed?

I have my PPEC admin set to :

Express Checkout: Require Confirmed Address - Yes

and had no issues until recently, a customer who I (assume) had a unconfirmed address tried to pay with with paypal..... he would go through all the checkout steps and upon "confirm order" it would loop back to the payment page.

Is this what happens when a customer has a unconfirmed address with this admin setting?

Just had a sale which went through ok, because the customer's address was confirmed. However as most of my sales are international and international customers cannot always confirm their address with paypal, There should be a notice/explanation during checkout that their address must be confirmed or they will be looped back to the payment page.

Is this the behavior of an unconfirmed address sale? No explanation and looping back to checkout? If so I will add a note.

I believe this notice for having a required confirmed address is presented by PayPal during the checkout process. This has been my personal experience with sellers that require this. The only thing I can think of as far as the looping behavior you descrived, is the customer clicked the return button and returned to select a different payment method. The notice should actually be displayed when the customer leaves your site and goes to PayPay to complete the purchase.

I know this isn't much, but I hope it helps in some way.