Google Chrome now supports receiving payments with PaymentRequest API using a list of 3rd party payment processors.
But I cannot understand if Google supports receiving payments with Google account only, without 3rd party processors, probably with Google Pay.
Is it possible?
To quote from the article you linked to (emphasis mine):
The Payment Request API is designed to be vendor-agnostic, meaning it does not require use of a particular payment system. It's not a new payment method, nor does it integrate directly with payment processors; rather, it is a conduit from the user's payment and shipping information to merchants, [...]
In other words, the purpose of this API is to allow you to receive payment information, e.g. a payment card number or some sort of payment token. It's not an end-to-end solution for payments - just an easier and safer approach to the checkout experience.
Furthermore, the Payment Request API is an open standard - it's not tied to Google and different browsers may have different implementations. Your second link (list of 3rd party payment processors) actually refers to Google Pay, which is a Google product unrelated to the Payment Request API (however, Google Pay can be used as a payment method through Payment Request API on supported browsers).