I don’t know if you learned anything else, but we recently encountered a similar issue on our end with a recent seller selling with our payouts system. A large number of payments from China were forced into PENDING_REVIEW. In our experience, after 24 hours the payment will clear, and PayPal will send a webhook to itch.io that will allow us to mark the payment as completed. The buyer will receive a purchase email with their download link at that time.
We did notice thought hat when the buyer completes a purchase that goes into pending, we show a message that looks like an error. We’re updating that screen to account for this case to instruct the buyer that their payment is being delayed by PayPal. Hopefully that will clear up some confusion.
Thanks