Your assumption of no output at all is not correct. We have very intentionally and carefully coded that to hide them with CSS precisely because it is absolutely essential to have that information there for Google and other SEO. It is very important. That is also why it is important to always provide a value for those fields in the WordPress Site Identity options menu instead of leaving them blank.
This approach has been carefully considered and discussed in great detail over the years by WordPress. In fact, there was a major change to the WordPress Theme API a few versions ago to be sure the site title and tagline HTML was properly handled and formatted to work best for SEO.