... as the adapter increases the distance between the sensor and the lens by ~10mm, does this effectively make my 50mm lens a ~60mm lens? Or am I just misunderstanding things?
You're misunderstanding things.
The Minolta MD/MC registration distance (or flange focal distance)--that is, the distance from the mount flange to the sensor, is 43.5mm.
If the lens is held closer than this distance, it will focus past infinity. If the lens is held farther away, its near-focus capability is increased, but it can't achieve focus to infinity (think: macro extension tubes).
Sony E-Mount's registration distance is 18mm.
Your adapter ring makes sure that the distance the lens is held from the sensor doesn't change. Its thickness makes up the 25.5mm difference, so that a Minolta MD/MC lens is mounted on your NEX, the lens's mount flange is still held 43.5mm away from the sensor in your camera, so that the lens can achieve focus to infinity.
However. This only holds true for simple ring adapters. If there are optical elements in an adapter ring, then the focal length of the adapted lens does change.
Some adapting combinations--where the adapted mount has a shorter registration distance than the mount being adapted to--require a glass element in the adapter to act as a short teleconverter so the lens can still focus to infinity. This type of adapter effectively increases the focal length of the lens, and reduce its maximum aperture, just as any teleconverter does. There are also the wide-angle adapters known as Speed Boosters which do the opposite--reduce the focal length and increase the maximum aperture.