The same three glyphs - kh - f - w - are required to pronounce the name, however it sounded.
There are innumerable examples from the archaeological record to demonstrate variant spelling of the same thing, though spelling is also constrained to some extent by convention and tradition.
See below. Six ways of inscribing the name of the same pharaoh, Ramses.
If it's OK to write the name Ramses in six different ways, what's the problem with the much more minor hieroglyphic variant spelling of Khufu?
Hieroglyphs are written in groups, accommodating aesthetic considerations and the limits of physical space by using different combinations of signs. For these reasons, words can be inscribed in a variety of ways.
Check out the variant spelling of the phrase "ma hrw", used to indicate a person is deceased. It was written sometimes with 7 glyphs and a determinative, 4 glyphs, 3 glyphs or 2 glyphs but always with 2 distinctive and recognisable elements to the phrase. Equally, by tradition the "ma" was never written out using two 1 consonant glyphs.