Wow, this is weird!
Both boxes are H20s; different software version. When you go to change the channel it momentairly goes 4:3 before the channel changes. When you switch say from 354 to 356 is 4:3 until the banner disappears then snaps to 16:9.
Format button is disabled when viewing 356 in auto expansion. If you go to 354 you're able to verify format as 1080 pillar box. ???????