That’s the first time for me to encounter the Nyquist-Shannon Theorem. Fortunately I didn’t have to know this in my GCSE additional math examination and med school MBBS exam
After reading your illustration and doing some online homework, I think what you mean is the sampling error issue, when trying to convert an analogue event (the time/oscillation of balance wheel) into a discrete value (the reading of chronograph hand).
Despite a 5Hz movement does move the chronograph hand in 10 increments per second, it’s prone to sampling error, which can only be eliminated by increasing the frequency of balance wheel oscillation by a factor of 2.
That’s my best understanding as a mathematical layman
Cheers, Henry