Is it just me or are square-ish resolutions pretty common and popular on tablets? Just look at any iPad, the screen ratio is ~1.3 or 1.4 to 1.
I think the common sense answer here (which is ridiculous since we don't even know what Samsung's real intention is), is a phone that's close to 2:1 and a tablet that's close to 1:1. No big deal.
To speculate more: phones have widened to near 2:1 resolution not primarily because of watching modern TV and film, but because that's the easiest way to expand the screen while ensuring the phone is easy to hold. It also works well with vertical scrolling activity.