Maxlength counter counts line breaks as two characters

This is the ordinary behavior of mb_strlen.

php > echo mb_strlen('foobar');
6
php > echo mb_strlen('foo\nbar');
8

https://stackoverflow.com/questions/68618268/mb-strlen-counts-new-lines-...

We are not going to change how Drupal core handles #maxlength.

Fine, but it would be nice to understand which javascript code does prevent to exceed the amount of typed characters. I would like to understand how the problem is produced.