This is what they(quickbooks chat/help) told me:

the PCI compliance email notice was generated by our back-end staff and it's a legitimate email notice. This is an additional protection for your QuickBooks Payments account and a heads up that it's an optional for you to sign up. Since your current QuickBooks Payments account is PCI compliant. You may disregard the email notice.

That said from my point of view given they are asking you to pay for service you don't actually need - its bad form.