After reading through all of the comments to this thread, I want to thank everyone for helping me think through the meaning and context.
I realize that "imperial India" conclusively means "British India" to me (and many others since this is undoubtedly the reference online as well). But I agree that "imperial" itself could mean the Mauryan empire or others (the meaning being "of an empire"). I guess my own negativity to the phrase "imperial India" stopped me from seeing this.
But this also makes me think, how words, phrases or history has different interpretations or meanings. It fits in this context because Buddha being mystic or not can also be debated in similar ways. We see what we want to see. The article trying to "un-mystify" Buddha made me biased against the author without me realizing it.