I guess people have different reasons for applying a topy (sole guard) but I like them because they protect the soles from water specifically. I like butyl soles, however, because the the oil is supposed to provide that protection thereby negating the need for a topy.
That said, never had to worry about broken glass before.
I never tried it personally, but I've heard that you can't apply topy to the butyl sole. It will stick for a bit bit but will come off eventually, due to the sole being saturated in oils. I am curious to see if this is indeed the case.