Not everything is for you.

But to answer your question, it’s nice to keep things grouped up by window, especially with a tiling DE, but to still be able to split/tile that workspace within the window and have the system treat it as one entity.

One project or subject per window. I use an extension called Winger in Firefox which essentially allows me to manage windows as tab groups; but it is also sometimes nice to use some kind of tab grouping (and now some split views) on top of that to help organize things within the context of that window.

I used to just be a “one windows with 600 open tabs, GLHF” kinda guy, but that is just a miserable way to live. Like i said, maybe all this stuff isn’t for everyone but when you need it, it’s nice to have - and for some things I appreciate a native implementation that we can extend with extensions instead of relying on every extension author to get right from the ground up.

Say you're redoing an image in photopea, you can have a split tab woth that image and photopea, so the image you're replicating is only there while you're trying to recreate it, and not any other tab.

I'd prefer it fixed at source too, but I do think there's a case for making it easy to, say fill in a form in one tab side by side with a reference tab if it's a 2 click sort of solution (even windows needs annoying drag and dropping with some randomness thrown in)

I'm unfortunately a slave to the three finger swipe (I think if that worked as well on Linux I would swap, tried a few third party things on Mint but it's not as good)

What's forklift bring to the table?

On Mac I have everything maximised, so I have to drag the thumbnail on top of another thumbnail, which then splits them unevenly, so I have to fix that, then to undo it you have to understand maximize one half (and to get back to where you started at least) re maximize and drag it back I to it's position. Plus there are the steps to take an existing tab and make it its own window in the first place.

Compared to like right clicking a tab and "show on the side" or however it will work..

yes, but that requires opening them, then resizing them and moving them to be beside each other; it's possible, but not convenient

By that logic we wouldn't need tabbed browsing at all, I remember browsing without it on IE6. :P