This is a big breach of trust in terms of Apple always being on the side of user privacy. If someone knows enough to install these firewall apps, then they know enough to figure out what they want to enable/disable even for Apple applications. If Apple thinks certain rules cause issues, they certainly could work with the developer of these apps to educate users of adverse effects when certain things cause unintended…
Your statement implies that it's difficult to install these apps. Installing Little Snitch is no different than installing any other macOS app. Also, this isn't specifically against Little Snitch, it's about any app that could potentially compromise a user's network traffic. Little Snitch is obviously a desired use of these features but how do you then differentiate it from the undesired uses?