luebking wrote:The kind exists because it's the typical behavior in webbrowser history buttons :-P

Yes, and that is bad usability. You can ask any usability professional about it. Many users probably find it out at some point (though I am very certain that if I ask my parents how to go back several steps, they will reply "I click the back button several times".

In fact, I just did a quick test with a member of my family. She eventually found it out, but only because she knew that Firefox had a split button there before and suspected that the function must still be there somewhere. Also, both Firefox and Chromium show a tooltip explaining what to do to bring up the menu.
We should not rely on such things.

I see no downside of actual split buttons. They worked well for years, why should we suddenly stop using them? Just because some designers felt that they somehow didn't look "clean" enough?

On desktop UIs, we have the space. Why not use it to make things visible?

Errrr.... I just pointed out why Qt (likely) supports this kind of button.

I can only assume that this is a specific design choice to unclutter the particular UI; the history access is rarely required in browsers - the "back one step" feature is hyperdominant (the back button is often even bigger than the forward button)
As mentioned, I consider this a "pro-feature" element - it should not provide access to any relevant features.