I think he’s refering to the bad reflections in UE4. It’s difficult to see small things in front of something that’s reflective, as it smeares the object to an unrecognizable mess. Especially the text render actor/component becomes difficult to read, and takes several seconds to fully “rest”, and become readable.
You can see an example of it here Unreal Engine 4 - Blueprint - Key Pad - Added hacking - YouTube at 1:25+. The small blue text on the key pad is all smudgy and difficult to read the first few seconds after it changes.