Well said.
"Tortoise" dealt with the general case thusly:
"Pretending that one can quantize a continuum rarely generates good results around the arbitrary boundary."
That pretty much says it all for this issue. Whether it is trying to draw a line that delineates modern humans from their more ancient ancestors, or planetoids from planets, or hills from mountains, they all fall into the trap of quantitzing the continuum. The boundaries are always arbitrary, and will almost always create debates regarding objects that are arbitrarily close to each other but which lie on opposing sides of the boundary we have arbitrarily imposed on the continuum to quantify it.
Do you think the declaration of a new species is arbitrary?
Darwin was aware of the issue:
Those who do not admit the principle of evolution, must look at species as separate creations, or as in some manner as distinct entities; and they must decide what forms of man they will consider as species by the analogy of the method commonly pursued in ranking other organic beings as species. But it is a hopeless endeavour to decide this point, until some definition of the term "species" is generally accepted; and the definition must not include an indeterminate element such as an act of creation. We might as well attempt without any definition to decide whether a certain number of houses should be called a village, town, or city. We have a practical illustration of the difficulty in the never-ending doubts whether many closely-allied mammals, birds, insects, and plants, which represent each other respectively in North America and Europe, should be ranked as species or geographical races; and the like holds true of the productions of many islands situated at some little distance from the nearest continent.Source: Darwin, The descent of man, Chapter VII.
However, something like this is to be expected and not really that remarkable at all but it seems to cause extreme headache to those who think that there must be a clear-cut answer to everything.