what was the term "techno" used to describe, though? the electronic dance music of detroit. then that term was applied to music directly associated with it, then to music directly associated with that. it's in these second and third phases that a more diverse range of influences come into play than whatever juan, kevin, derrick n' friends were listening to in the 1980s. but techno as techno still stems directly from the detroit tree, and not so directly from that other range of influences.
it's foolish to think there was george clinton and kraftwerk in a few guys' heads and that's where all today's techno music exclusively comes from. but it's too revisionist to go so far in the other direction as to forget that the music called techno comes from detroit; that without detroit, we don't have techno; and that as powerful an influence on techno's development that things like EBM, industrial etc. have been (and arguably more so than detroit stuff in certain corners of techno), they're just not as directly and generally influential on the genre as a whole.