PLL jitter and 500uV/div are not related, so I don't understand why the quote is about PLL and the question is about 500uV.
Anyway, I have the 500uV installed, and it always worked (as far as I can remember). The only problem with it was that if you don't recalibrate after installing the 500uV/div option, then the trace can have a big offset on the screen.
Even if theoretically the 500uV option kind of "works", the analog front end in DS1054Z is very noisy. For 500uV/div with no probes attached I have a noise of about 2-3 divisions pk-pk depending on what channel I am looking at, so it's almost unusable.
If you need an oscilloscope for small signals, then the DS1054Z is not the right tool.