How humans are still evolving

[I_am_not_mafia]

There is also though a historical use of the word milk to refer to any liquid that has a milky look and feel. After all, Coconut milk has been called that for a very long term. Pretty sure it's been used for describing opium in the past. Maybe the noun milk should be considered as deriving from a description instead.

If so then it's actually historically consistent to refer to Soy milk as milk, even though it's not the same kind of milk as milk.

Historical consistency has fuck all to do with accuracy.  If people had been referring to dolphins as daffodils for the last thousand years - all the while knowing good and goddam well that they aren't the same thing -  it would still be wrong to do so.  Same with milk.

My point is that referring to something as soy milk is accurate because it is referring to its texture, not why it was produced. If 'milk' refers to an opaque white viscous liquid, then lactation is a milk as well as the juice from a coconut. Your analogy with daffodils and dolphins fails for this reason as one cannot be considered a superset of the other.

Context also matters. If you're referring to soy milk when talking to a biologist when talking about child rearing then it's not going to be accurate, but it is valid when shopping for a milky liquid. Basically it comes down to whether the term is useful or not. In the same way that chemists know that glass can be considered a liquid but no one will know what you are going on about if you refer to windows as vertical clear liquids.

And historical usage does have a major effect on how science talks about something. Significant work goes into making definitions less ambiguous. For example whether Pluto is a planet, what emotions are, what granite is etc.