A blog post means it’s real:

An official* logo for HTML (from @sstephenson)

https://www.zachleat.com/web/html-logo/

An Official* Logo for HTML—zachleat.com

A post by Zach Leatherman (zachleat)

Zach Leatherman
@zachleat @sstephenson Would vouch for 4em width and height.
@nilsmielke @sstephenson I do think that would make the text be more readable when scaled smaller 🤝 (shipped)