I disagree completely with your first gif/flash showing 16:9, 16:10 and 16:12
16:9 is more letterbox than 16:10. But you cannot think of 16:10 as less, cutting off the sides. No. 16:10 is everything and all 16:9 offers PLUS extra pixels/FoV up and down. It's simple. They are both 1920 in the x. One is 1080 in the y, the other 1200. Clearly, one can show MORE than the other. The gif/flash is faking/falsifying the results by pretending the y is the same but x is less. How disingenuous is that?! Horizontal FoV (measured as an angle) has changed between screenshots!
... some things in life just drive you bonkers. Especially the rubbish you see in forum posts