I was recently in a ranked game on Ana. After sleep darting my accuracy seemed fine but I checked once again later in the round and my accuracy spanned through numbers such as 133%, 200% 500$ and -200%.
I have seen this too as an ana main. None of these numbers are reasonable no matter how you calculate it. Is and are always hit sleeps/thrown sleep darts. The ow team probably should be back to school to learn how statistics work