A Product Variation should inherit tax attributes (Taxable, Tax Class) from the Configurable Product.
I think it should, but it doesn't in SVN r2015.
There may be other attributes that should be inherited (overrideable, of course): weight, image, others?
I haven't thought this through, but my first expectation was that a Product Variation would inherit ''all'' attributes of the Configurable Product, which would be overridden as necessary.
This is minor-to-trivial, because with extra user work it can be worked around. That workaround does make user errors and omissions more likely.
Reported by Ned