Ah! I am a beginner, and use a much thinner quilting cotton. To prevent the glue showing I have to fill with mix of acrylic medium and starch paste (haven’t found a ratio I really liked), or to back the cloth with paper. So to me your casing looked like witchcraft! I really like the etching effect. No idea how it’d work in practice, but it seems like you could make some gorgeous illustrationy covers by going over the cloth multiple times at different strengths for different values.
In general librarians are looking out for their communities the best they can with the meager resources provided. Libraries barely get funding to keep in books, much less security guards and lawyers. Who would enforce the age gating? Maybe it’s an acab type of town, and closing the library for a spell is safer than calling the police. From the article they planned to put cameras in the library, which would help find-out come home to it’s fuck-around.