This is a fair point. In recent years (before Brave supported tabs, but after I left Firefox), I had to use a single window because the TST-style tab manager sat beside it in a separate window. This was annoying enough even with a single browser window, and it was unmanageable with multiple windows.

But now that I'm using native tabs, it is much easier for me to use multiple windows because the tabs are attached. Thanks for pointing this out!