I have added un 2.5 inch 2 Tb Seagate HDD for Time Machine in my dock.
It works fine, this HDD is 7 mm height. It's not possible to add a higher capacity because there is not enough space
in height for bigger HDD. All the other HDD drive on the market are higher than 9 mm high !
For me the SATA drive is good for Time Machine, but we need to be able to use bigger HDD than 9 mm height size.
If Trebleet can take this into account for their next Thunderbolt 4 Dock it will be perfect.
I don't know if it's because I have installed TechTool Pro with the SMART driver for USB. But I am able to read all SMART
informations from this drive, which is connected over USB 5 Gbit/s via a JMicron JMS 578 IC.
You have only 5 Gbit/s bandwidth for this drive, no worry for HDD but if you place a SSD it will be limited to 5 Gbit/s instead of 6 Gbit/s SATA-III bandwidth. But I think there is no IC on the market to provide USB 10 Gbit/s to SATA 6 Gbit/s.
There is also a cool software DriveDx which allow you to check all SMART information from your drive and it works well
with my SATA Seagate Barracuda 2.5 inch HDD drive.
TechTool Pro is also able to monitor the HDD drive temperature which is not always the case with USB drives.