Thanks, I can confirm that all the windows I posted screenshots of above now have maximizers in Quantal. The package downloading window (which I only mentioned) also had one, but there was one still missing it: the ’Applying Changes’ window. That one also sometimes gets quite a bit of content with the ’Details’ pseudo terminal. I didn’t post a screenshot of it above, I’ll do so now below with Synaptic 0.75.12build1 running in a VM.
Also, I did notice that the maximizers were missing from all of the fixed windows too when running Gnome Classic (No Effects). But I guess that’s going the way of the dinosaurs anyway so it probably doesn’t matter. With Gnome Classic (without ”No Effects”) the maximizers were there, as with LXDE and Xfce. (Non-fallback Gnome 3 was misbehaving too much to be able to tell either way.)