Partially true.

Yes, there's definitely very few UI changes between D7 and D8 ... so sitebuilders should feel right at home.

However, everything has changed in the codebase, so developers have a lot of learning to do.

Actually, D8 adds a few (optional) modules which add some nice UI flourishes to simplify things for administrators and content editors. The stock administration menu module has been greatly improved and made more user-friendly out of the box, and there's many places where you can now do in-place editing of content. Also, everything is responsive out-of-the-box, including the content editing forms.

Also, Overlay is gone. (Sorry about that showing up in D7. Some of us tried to stop it, but…)