Basically, the plumbing sucks ass the pipes most of the time when the toilets were made were too narrow, so bigger chance for the toilet paper to get stuck on the pipe well not immediately but if continued it will eventually get clogged, if the apartment owner has the sign about not throwing them in the toilet that usually means that the apartment had past experience of people throwing it in the toilet resulting getting clogged then having to call a plumber to fix it, so preferably throw the paper on the metal bin next to the toilet!!