By hard pipe, I assume you mean non-flexible metal conduit. I agree that's needed for home runs, and most of the wiring. But are you asking if the actual connection to the fixture needs to be nonflexible?
I think it is pretty common to use a short flexible whip to light fixtures. I assume the electricians consider this as meeting the exception in 517.30(C)(3)(3)(c) which basically says "flexible metal raceways where necessary for flexible connections to equipment."
Steve