The lack of surface conductivity is not the criterion of topological insulator presence in this arrangement. The topologically insulating surface must be formed with monocrystal cleaved along certain lattice planes and its scratching or monocrystalline samples actually leads into increase of conductivity with respect to bulk. The ferrites get often doped with many impurities and their resistance depends on it, so you can hardly guess the material from conductivity. The hard ferrites are generally of low conductivity, the sample of "conductive strontium ferrite" presented in the video could be formed from nanodust iron for example.
The demonstrator is not John Bendini - or even Bedini - but Neal Weber