I'm sure Grammarly won't test positive as I've already done some tests, also several other tools are in the clear. These tools that detect AI content only search for patterns that are proper for AI and how likely the content is to fall into those parameters.

Wordtune might give a positive result, as I have not tested it so far to see if it does, https://www.wordtune.com/ua/ai-writing, but the webpage does say that wordtune uses AI to change its content to look and be more AI, admitting using it is to trick yourself into thinking you are in the clear, but it is still AI doing it.

This AI detector is from open AI itself, so it is quite hard to say it is a false positive, they are the creators of ChatGPT, and use their own database to determine if something is, or it's not AI content.