Mysterious yellow text in monostyled blocks in Notes

I was revisiting my old notes that I wrote in leisure all for fun when I saw that in two of the code blocks with the word "angle", the word "angle" is coloured yellow. No, it wasn't a link. Also, the word "math" in a code block was covered with a red dotted line (strikethrough).

I did restart the app and same result. I tried writing these words on a different note and nothing like this happened.

How are specific keywords yellow? Is this some sort of a new syntax highlighting feature secretly added?