I believe Gruber argues completely the opposite: that the recent changes to add features like split screen make it more confusing (e.g. the example of his mother getting stuck in the split screen and calling him). He continues in the very article we comment here (emphasis mine):

"if I could go back to the pre-split-screen, pre-drag-and-drop interface I would. Which is to say, now that iPadOS has its own name, I wish I could install the iPhone’s one-app-on-screen-at-a-time, no-drag-and-drop iOS on my iPad Pro. I’d do it in a heartbeat and be much happier for it."

And I think that should be a configurable accessibility option: to have UI completely discoverable and non-stuckable, even if some "so-called-Pro" features need more steps (or can't be implemented). Or even better and safer: that should be the default, with "advanced" shortcuts as an opt-in option.

The interface should by default to never bring users to the point where they can remain "stuck" in some mode from which they can't get out.

Steve Jobs understood that that 100% "discoverability" and "non stuckiness" must be the default UI, that's why Gruber would like to switch back to that older ideal.

And Steve Jobs was old enough to learn that much earlier: that the "modes" are bad and that good UI doesn't require one to do some magic to switch between them, as it can be summarized in the joke: "How to Quit Vim and Exit the VI Editor — the most popular Stack Overflow question -- and I'm using vi last two years because I can't figure out how to exit it."

Even these "visual" UI changes that made the UI more "Ive-conform" (removing buttons and having only text) made the UI more confusing for anybody not trained and retrained. The back "button" in the apps was drawn as a button when Jobs controlled the UI. Then it got to be switched to just the < sign, which those who don't frequently use the UI never understand to be anything more than a meaningless symbol on the screen.