I tried it myself and the problem was solved. It was my folder path that was wrong.
If you don't understand the description of "Mac OS: ~/Preferences/Houdini/XX.X/" in the document, just enter "~/Library/Preferences/houdini" in "Finder -> Go to folder".
You will see the Houdini version folder.
Then, follow the instructions in the document to create a packages folder and set up a json file.
After restarting Houdini, you can see MOPs Tools.
I hope this helps Mac users who are confused about this.