TIL, but still: the lecturer changing their book preference at the last minute still seems different than "you have to use edition 15 of this book (which came o

TIL, but still: the lecturer changing their book preference at the last minute still seems different than "you have to use edition 15 of this book (which came out 3 months ago) which is exactly the same as all the previous editions, but the exercises are rearranged, so you'll get confused if you use an older edition", which - if I understand it correctly - is what seems to happen sometimes in the US.