In MDL-77895, H2 was removed from Tiny, likely because that is what it was in Atto. However, upon further investigation, there are many activities where only an H1 is present on the page, and skipping to an H3 because it is the next header option in the editor is causing people who are in the know about accessibility to have to either add H2 manually in HTML source code, or jump to an H3 and risk reports from end users.

This should likely be resolved in any version currently receiving bug fixes.