href="https://wordpress.stackexchange.com/questions/350287/./contact-page"
- if you’re on the homepage (
/) this will become:/contact-page - if you’re on another page named foo (
/foo/) this will become/foo/contact-page
This is due to ./ being a relative path. To avoid struggles like this, the method via home_url() is preferred because it creates absolute links/paths that will work from anywhere you call it.
Note:
You could use href="https://wordpress.stackexchange.com/contact-page" which is relative as well, but only to the domain and not the current page. However I can’t tell you why WP rather uses and stores absolute URLs.