I do not get a sense that these posters are incomplete or restrictive, except in the broadest sense that any work which attempts to teach a topic will necessarily not be able to capture the entire breadth of what is possible (and doubly so for a "cheat sheet").
The author of these posters is a theory professor, and the rules he describes here are perfectly fine cheat sheets, in my opinion, for students. They describe idioms that students will likely run across, both in the repertoire, or in their assignments. I don't think there is anything wrong with that, and I'm not sure the author is claiming that this is intended to be a prescriptive set of rules for composition. Just a useful one in a classroom setting where you probably need to start out learning some things, prescriptively, when starting out.
I'd say, take these PDFs for what they are - a learning tool for music students.
Species counterpoint was exactly that - a set of rules intended to be a pedagogical tool.
I don't disagree with you. But when these get cross-posted to sites like this one and lack the context of what they are, they often lead to really unproductive discussions about how broken music theory is or how there are better ways of understanding things or how they are fundamentally incomplete. You can see a lot of that happening in the comments of this article here. So I was simply trying to provide a little more background about how to view these kinds of tools.
This is my sole frustration with most composition-related libraries: they misspell pitch classes because “they’re the same note.” It isn’t just mathematics!
The author of these posters is a theory professor, and the rules he describes here are perfectly fine cheat sheets, in my opinion, for students. They describe idioms that students will likely run across, both in the repertoire, or in their assignments. I don't think there is anything wrong with that, and I'm not sure the author is claiming that this is intended to be a prescriptive set of rules for composition. Just a useful one in a classroom setting where you probably need to start out learning some things, prescriptively, when starting out.
I'd say, take these PDFs for what they are - a learning tool for music students.
Species counterpoint was exactly that - a set of rules intended to be a pedagogical tool.