P2723DE, USB-C Daisy Chain, MST limitations?

I have 3 of the P2723DE monitors in a daisy chain over USBC. The x3 1440p displays combined bandwidth is within the DP1.4 spec, and I have had multiple Dell and CDW reps tell me that the config would be supported. However, it seems that when running the daisy chain, I can only get 2 at full 1440p 60hz RGB 4:4:4. As soon as the 3rd is in the chain, all resolutions drop to 1920x1200.

The only way I can manage to get all 3 at 1440p 60hz is to drop the pixel format from RGB 4:4:4 to YCbCr 4:2:2, which makes certain text blurry. Since YCbCr 4:2:2 (~3.75Gbps per screen) used less bandwidth than RGB 4:4:4 (~5.63Gbps per screen) it made me look into how many DP lanes were being utilized over USBC.

My laptops (tested with a 2024 Lenovo P14s and 2024 HP Envy) shows only 2 DisplayPort lanes are being utilized instead of the full 4 when connected to the P2723DE. I set all three of my P2723DE monitors to use "High Resolution" and "MST On".

The P2723DE manual specifies the monitors support DSC HBR3 as well, which would put the total bandwidth at ~15.93Gbps uncompressed or DSC at ~5.97Gbps, both which 4-lane DisplayPort can handle. 

Is 2x DP lanes over USBC a limitation of the monitors?