Yes, in Windows since 8 (i think) if you doubleclick on the top edge (where the mouse cursor becomes the top/down arrows) you maximize the window vertically (its width remains the same as it was).

> What is it about the freedom to move windows anywhere that is particularly appealing? I ask because I'm trying to get a bit of design perspective.

It is really what you wrote: being able to put things wherever i like and at the size that i like them (the size bit is important since with tiling you can only resize on one dimension), but also because i want to be able to overlap things when that makes sense.

> I think I'm trying to rank the un/usability of tiling versus MDI window grouping (which I can see breaking down outside of carefully scoped situations).

I think that it isn't that different from regular tiling vs floating/overlapping window management (regardless of MDI). But this might be my own bias since i also prefer overlapping window managers to tiling window managers for similar reasons.

> Interesting! I'm curious why. The different aesthetic of a bigger icon? (The task buttons did also have an app icon)

Note that i'm talking about the MDI subwindows here, not the taskbar at the bottom of the screen. Here is an image showing what i mean:

https://i.imgur.com/Asi9rk8.png

On the left side is the Windows 3.1 File Manager and on the right the linked File Manager (basically the same program but improved a bit) running in Windows 10, in both cases with three MDI subwindows open, two of them being minimized at the bottom left area of the main window.

On Windows 3.1 the minimized MDI subwindows have a clear icon showing what exactly they are and a clearly visible caption. On Windows 10 the minimized MDI subwindows use a "tiny" framed appearance instead of an icon, the caption is not visible at all and you basically have no idea what you are looking at. Note that on Windows 95 and NT4 (which used the same look/theme) things were slightly better, but not much:

https://i.imgur.com/5pKYvcv.png

Personally i think the bigger and clearer icon, the caption below the icon and the lack of a border/titlebar/buttons/etc that in Win95 and later only waste space is superior both from a visual and from a practical perspective.

> I'm guessing that infrastructure was primarily built out at all for Program Manager.

In Windows 3.1 everything used that, even the Program Manager was an MDI application and the groups were just minimized MDI subwindows. In Windows 95 they changed the look for the minimized subwindows to use the look i show in the shots above instead of using icons, but i remember reading in the win95 visual design guidelines about icons in MDI windows that were supposed to be about something else. However i haven't seen any program using that and the code that previously (in Windows 3.x) created minimized windows as icons, in Win95 created minimized windows as those long bars.