Hello mace_wuu,
This doesn't appear to exist at the location from the kb article nor from the Health UI Build Recommendation check - it came up with a colleague recently but I didn't think much of it as it was a nested lab with no internet connectivity - I will aim to take a look into this from my side but I would advise you also open a Support Request in case logs etc. are required.
sk84 - from what I have seen this doesn't appear to be HTML5/Flex Client specific, though if you have screenshots from where you found it in the HTML5 Client please do share them.
Bob