U2720Q, MacBook Air, USB charging issue

I've been using the U2720Q connected to a Mac Mini for some time and haven't experienced any issues.

However with a MacBook Air connected via USB Type-C I've noticed the USB A charging port on the side of the monitor will not charge any other device (e.g. phone, provide power to a wireless charging pad, etc) when the MacBook is connected. When you unplug the USB Type-C cable from the MacBook Air, the USB A port then starts delivering power. I've not yet tried to transmit data via the port when the MacBook is plugged into USB C, so this is only about power delivery.

Wondering if this issue is common on both Mac or Windows, or is limited to MacBooks charging/connected via USB Type-C? I've seen some similar posts regarding Macs, but the U2720Q is listed on the Dell site as working with Macs.

It's as if it can only charge one thing at a time and USB Type-C has priority over USB A. I also have data set to USB 3 on the monitor (data over display priority, so that may also be related).