Actually disregard that. I never used scalar values. Thought it was equivalent to [[scalar],[scalar]], but this is not at all the case: http://docs.scipy.org/doc/numpy/reference/generated/numpy.tensordot.html
"""The third argument can be a single non-negative integer_like scalar, N; if it is such, then the last N dimensions of a and the first N dimensions of b are summed over."""
So kept it at 2 and updated the doc of both tensordot and batched_tensordot.