If they’re competent to go so, who gives a aerial wank what the nanny state says? Talk about retarded bureaucracy run amuck. Liability? Who’s suing whom?

If you’re paranoid, just have them buy 10% extra tile so you can fix it if anything cracks in future.

I see it’s an issue in CA, but in NJ and NY, no such thing is needed. When my family needed a bathroom floor redone, I hired a friend’s brother who started a tiling business out of high school. He did fine.