Complex sentence: A dance piece will be called "physical theatre" because it includes elements of spoken word, character, or narrative; it is theatrical and physical but does not necessarily share anything in common with a potential (and nascent) physical theatre tradition.
Split into simpler sentences: A dance piece may be called "physical theatre" simply because it includes elements of spoken word, character, or narrative. However, although it is theatrical and physical, it may not necessarily share anything in common with the physical theatre tradition.