U2723QE: MIRROR on M1 Pro MacBook through DisplayPort daisy-chaining?

Hi! I have a U2723QE (USBC monitor with built-in KVM switching). I also have an older "dumb" monitor with plain old HDMI and DisplayPort inputs. My goal is to connect a Thinkpad and a MacBook to both monitors, and use the KVM switch on the U2723QE to switch both screens + peripherals between operating systems.

I understand due to Apple's arbitrary software restrictions, they have failed to fully implement the DisplayPort spec, meaning that extending displays via daisy-chaining is not possible. However, on the Thinkpad it works like a charm. The compromise I had in mind was to simply abandon the idea of extending the displays when using the MacBook - I could deal with them being duplicated/mirrored, or I could just turn the second screen off while using the MacBook. 

The MacBook is connected to the U2723QE via USBC, which provides data, charging, and a display connection with a single cable. The Thinkpad is connected via DisplayPort in. U2723QE is daisy-chained to the second monitor via DisplayPort out. The KVM switch is correctly configured to switch between these inputs, and it's working fine.

My problem is that the MacBook does NOT mirror the first display on the second when they are daisy-chained together. Instead, both monitors just power-cycle repeatedly until the daisy-chained DisplayPort is disconnected. It looks as if it's repeatedly trying to establish a connection to the second monitor. This does NOT occur if I turn off the second monitor before switching the input to USBC.

Am I incorrect in my understanding that the MacBook should be able to mirror the first display via DP? 

Again, I understand that Apple stinks and they won't support the extended display. I'm just wondering why mirroring doesn't even work.