It will definitely change the taste - for better or worse only you can judge that. You might like it.
But by using oil instead of butter, I doubt very much you will get fluffy or flakey biscuits. I believe ATK say in their description "when the bits of cold butter melt and create steam—thus a flaky biscuit."
They are still creating the steam with the melted butter and the buttermilk.
I shouldn't think that the oil will create any steam at all.