>>513891703
>groups must always be well separated
That's a completely false assertion and only the statistically illiterate fall for it. Midwits simply find OP's phrase appealing because it works on most people, who are the statistically illiterate.

There are literally millions of species which have greater within group variance than between group variance. Pic related. Put simply, overlap does not mean the groups cannot be separated, the groups clearly have different points around which they cluster.