I got a client that wants to stick with the classic editor and wants to have unique headings on the content (meaning that, for example, an H2 should not appear more than one time in the content). To facilitate things a bit, I have set headings H2 to H6 to be the same font size. It works in the front end but not on the backend as the headings are rendered in different sizes even though I have adjusted their sizes accordingly in the Customizer.
Is that something that can be fixed?