The black square is strictly for LOCKING the vehicle. The UNLOCK sensor is on the inside of the door handle. The unlock sensor is not visible, it's just the inside of the handle. So, when you grab the handle as is natural and your fingers contact the inside, the unlock is activated.Loving mine. 
It's almost perfect except for two things. MFT doesn't like either of my USB sticks - rather, it liked one for a couple of days and told me it was unsupported ever since.
And sometimes when I use IA to unlock the driver's door (by holding the handle and black square), it chrips as though I was trying to confirm it was locked. I've actually no idea how it would know whether I wanted to unlock or confirm it was locked! It gets it right most of the time.