You're right it was WordPad he tried.
A super basic text editor is available anywhere. He's comfortable with many of them when editing other things (like vim/nano/ed on Linux)
He just likes Notepad for his personal use. Now that you mention it I do believe he used Notepad++ at some point (only 3rd party editor he's tried). I don't remember at what point he dropped it but he didn't use it long.
Like you said, with Windows 11 replacing Notepad with a rewritten version, he's probably going to have to switch to Notepad++.
I was hoping he'd just switch to Linux. Even tried baiting him by giving a pre Linux installed fully configured laptop with a beautiful OLED panel and great keyboard. He loved the hardware and reinstalled Windows.