Current RDP target windows version as below
Microsoft Windows [Version 10.0.19042.1645]
The Retina display optimisation feature worked perfectly until resent Windows update happened on target laptop. Everything now becomes native 4K resolution instead of nicely scaled UI previously.
Manually setting resolution in Microsoft Remote Desktop is kind of workaround, but if doing so, the UI and font appear blur and not-so-smooth as how Retina display optimisation worked.