I agree to a certain degree on the multitasking, but for me the strength of a tablet is it‘s a great focus device. All this multi windowing is just distracting. Also “multitasking” starts to fall apart on smaller tablets Like the tabs S9+ or iPad Pro 11.
And when you use the tablet in full screen, 4:3 is better for everything except video watching, including spreadsheets, as you can see more row content on a taller screen.
There’s a reason many prefer the taller screens of the surface laptops for example.
Monitors are usually bigger screens, and then it starts to make more sense to go wider.
I always thought the 4:3 ratio on ipads was better for everything, trust me Im a big fan of the ipads aspect ratio. Even when I bought my M1 ipad in January of 2022, and the S8 series came out shortly after. I really considered switching to the S series. My Best Buy only had the S8+ on demo so I was only able to judge off of that and I didn't like it because like you said, it felt too tall and too narrow. So I kept the ipad and I never got a hands on experience with the S8 Ultra and I never bought one because I just assumed it was more of the same.
But when I got the S9 Ultra recently, it completely changed my opinion on all of that and I think it's mainly due to the larger screen. It makes all the difference. On the S9 U, because the screen is so big, you see much more content in portrait and slightly more in landscape compared to my Ipad 11". I compared them side by side once I got my preferred scaling settings dialed in. After using it for everything since then, I much prefer the 16:10 on the S9 Ultra for everything. The ipad 11" feels tiny in comparison.
Ive also used 3:2 Surface Pros for many years and I loved the aspect ratio. I love that aspect ratio so much that I even considered buying a portable 3:2 monitor for my laptop but they're very hard to find. Before I bought the S9 Ultra, 3:2 for portable displays was actually my preference over 16:10 or 16:9. I really value the vertical space.
But now after owning another 16:10 device, I see all the benefits. My last device that I had that had a 16:10 display was a laptop from over 15 years ago.
I feel 3:2 went perfect on a smaller screen in making it feel that much larger, such as the Surface Pro. But I don't think I could even go back to a 3:2 screen on a large device like the S9 Ultra. So my point is, I think the larger screen size on the S9 Ultra has a bigger effect than the aspect ratio. It doesn't make the device feel too tall or too narrow at all.