It's mostly only sorta true.

The thing about the scratch marks though? It was more like 1 in 5, not 1 in 25. After the plague, they were in such a hurry to get em buried that they wouldn't bother to hold a mirror over their mouths first. There were thriving businesses that sold bells on pullchains that were installed in the coffins and ran up topside to the bell. Also people left food & wine in tombs incase someone found themselves locked in wearing their best suit or dress with pennies over their eyelids.

The thing about bathing was they considered it to be lethally dangerous. The association between getting wet and 'catching your death' was so close that most people avoided bathing at all costs and opted for perfumes or body oils.

Another thing: The water was so full of human and livestock schit, drinking water was even more dangerous as bathing in it. Beer, mead, & wine were consumed by even little children because everything else was polluted. There was no real concept of sanitation and disease was thought to be brought on by demons and/or God's wrath.