My guess... When HDR was new for Samsung TVs it was enabled by default but there was a selection to disable. In later TVs I guess Samsung thought HDR was so great that everyone would want it all the time... so they made it automatic with no way to turn it off. I notice now through Windows Display, the TV is running with SDR and will now run @ 60Hz. I see my computer monitors are running in SDR also... I don't know whether the monitors can't do HDR or whether W10 is controlling that to make it run in SDR. Lots of people have complained that they can't run streaming video properly in HDR and look for the way to disable it in Netflix, Hulu, et al. Critics claim HDR is the greatest thing since 4K, but it requires more bandwidth/horsepower/resources... something(?). Apparently not all monitors/TVs can handle it at 4K res.
I got an Acer DM431K monitor, 42.5" for $600 only. It has been running fine for > 1 year. Nowadays computer monitor price is getting very attractive. I have it in portrait format to display all the trading ladders. With a proper monitor, you don't have to worry about those frequency problems.
There are 4k, 43" TV monitors one can use for computer display... for $239 and up. Perhaps that's good enough reason to go that route rather than $600 for 43" monitor... I even recently saw a 50" 4k monitor for $200!
I doubt there is significant distinction between 4k monitor and 4k TV in display quality. My 43" Samsung "TV as monitor" has sharp, clear graphics and text...and vibrant colors.