You need to uncheck Constrain Proportions. Otherwise, you will always have a rectangle of the same Aspect Ratio.
Now, going Square will result in a change in the way subjects look.
If you want Square, but with the proper look, investigate the Crop Effect, and the fixed Effect>Motion>Scale (what you are using now, but with Proportions Constrained).
Hey Hunt!!!! Fancy meeting you here! Are you planning on a nice bottle today with dinner?
I can ALWAYS depend on you buddy... It seems as if I have an uncanny talent for overlooking things in Adobe... LoL
* just to keep everyone on the same page, in case anyone else see this it may say 'uniform scale' also...
I am ALWAYS planning on a nice bottle of something with dinner. Last night, it was a Cakebread Cab w/ some steak, and if I heard correctly, we're having Tuna. I am thinking of a Bottle of Benovia Sonoma Coast PN.
As for overlooking things in PrPro, it happens to all of us. I'll work with some feature, and assume that I have committed it completely to memory, only to need the manual, with I revisit that feature in a few months - "hey, how did I do that???"