What problem does this address?

Currently, with FSE, you can alter aspects of your site you couldn't previously including the Site Title. As a result as part of FSE Outreach Program testing, the following feedback was raised:

Also, I wasn’t sure about being able to choose h2-h6 and p for the site title. I think it is fairly common practice to set h1 on the front page, and div/span on other pages. If a person who is using FSE is a developer, then perhaps we can leave it to the developer to make the decisions (and should be aware of semantics and web standard). But if one is non-developer, then may be it is more friendly to limit the choice, or just have h1 and may be allow to choose which tag for non-front-page.

What is your proposed solution?

Perhaps similar to how we show warnings for picking low contrast colors, we could show a nudge to encourage people to make good decisions around semantics for blocks like Site Title.