The "problem" is that people—the ones that actually care whether or not something was written by AI—don't just want to spot text that was generated by AI (like in your examples). They also want to spot text that was re-written by AI.
Before I explain the great big difference (which you probably already understand, just bear with me), know that the folks who are most up in arms about it are authors. They see their art as sacred. An ancient tradition of storytelling that deserves respect not for its output, but for the act and talent of producing it. To these folks, the very concept of using AI to generate or modify text in any way is against their religion.
Now for a real world example that would violate their principals that wouldn't bother normal people at all: A beginner or someone who's just terrible at storytelling has a story in their head and they do their best to write it down. It might look like this:
MC: "You call that a knife?"
...and so on and so forth, with poorly written descriptions of scenes, run-on sentences, etc. Then they feed that script into AI and go back and forth until they have text that they like.
To traditional authors, this is straight up EVIL. It's against everything they believe in! That person didn't write the story! They just came up with a poorly-written outline and the AI converted it into something more digestible.
Normal people will read such a story and—if it was created with the latest AI models—will never know the difference. It probably won't be a fantastic story or super well written but it will be passable. Even if they find out the process that went into it they won't care. And that pisses off these authors the most.
There's degrees to this, too: If you wrote an OK story, AI can be used to make it better. You can feed it multiple paragraphs and have it analyze the flow and offer simple suggestions for ways you could re-word sentences to improve them. Basically acting as a personal editor.
Is that "written by AI"? I would say, "no" but traditionalist authors would disagree. To them, any use of AI to write your story violates the very nature of storytelling.
...and it pisses them off to no end that you can't just run texts generated in this way though a program to tell whether AI was used in its creation.