Apple calls the green button “zoom” in their documentation, but its default function is fullscreen, not zoom.
I've always found that a bit disorienting. I guess Apple just decided that "zoom" is better as a name because it's one short word instead of two.
Yes, they switched the behaviour shortly after they added the full screen mode merging it with a separate full screen icon they had introduced. The old behaviour is retained by option clicking the green button. It's annoying and I wish they kept it as was.
Also you can double click the edge of any window to extend it to the edge of the screen.
I really don’t get the obsession for tiling windows personally. It’s not part of my workflow.