This wouldn't work as you could have a semicolon in a string, to handle that you would need to know when you're in a string, and due to the existence of backslash escapable quotes in strings, you can't do that with a regex*
*A real Regular Expression. The extended versions with e.g backrefs can. But they're also Turing complete anyway
Actually, I think that the grammar for a C string with escapes characters is regular. The only bit I am worried about are the back-slash octal and back-slash hexadecimal notations. But they are not relevant if you want to detect escaped quotes in strings.
Sigh. My point was that it _feels_ like this because the tutorial does not actually do an actual compiler's work. It is a quite simple rewrite to a very similar language with the same level of abstraction. No language constructs have to be compiled, i.e., to be automatically reimplemented in a target language which doesn't have this.
Now, if your only concern is that everything that people feel and express have to be technically correct, well, have fun in your life.
However, if you actually want to learn about compilation it would be a better exercise to use way simpler languages but actually do the work, for example: write a simple stack VM which can only do NAND operation, and then parse and compile to it a boolean expression language which has 0, 1, not, and, or, xor. There you will need to build a simple AST and traverse it one time to translate the basic boolean operations to use only nand, and then a second time to compile the nand expression to your VM's assembly language.
*A real Regular Expression. The extended versions with e.g backrefs can. But they're also Turing complete anyway