The other issue with USB PD without a battery is that most chargers with multiple ports will drop the connection and renegotiate if any of the ports are plugged or unplugged (whether they need to in order to supply the new device or not).
(Relatedly, there's an empty niche in the market for a USB-C power bank that can act as a UPS: able to charge and discharge at the same time without interrupting the discharge port when the charge port is disconnected)
(Relatedly, there's an empty niche in the market for a USB-C power bank that can act as a UPS: able to charge and discharge at the same time without interrupting the discharge port when the charge port is disconnected)