Your toilet brushes probably don’t have anaerobic bacteria spores on them. To be clear, I think this is properly gross, but I also acknowledge that to some degree this is a marginally irrational preference for keeping food and poop separate. In all likelihood, there is no actual risk of disease from this practice.
I have had my road replaced three times in 5 years because first they installed new gas lines, then they installed new water lines, and that damaged the gas lines so they needed to fix them in a bunch of places.