Not seen any issue in my use cases at any sizes. No need to waste time on manufacturing scare stories. This thing works fine. I'm sure a professional designer would want and need to use the LG 5K screen- I have one at my desk at work and it's even better - but honestly this 4K one is fine.
There’s tons of reports of UI lag and stutter when using scaled resolutions with the 2018 Mini. Especially with the 8GB base model.