Some people claim that filing the springs of the micro-USB plugs will reduce the rick of breaking the socket. Is there any real evidence to support that hypothesis? Any factual data from an engineer who tests there things?

The springs in the micro-USB plug apply a force *inside* the socket, holding it in place.
Is the logic that this increases the force needed for insertion and removal?
It does not feel excessive to me, and because the socket is very low-profile, and snug to the board, the force transferred to the surface mount from normal insertion is small. And Nokia would have tested this with thousands of robotic insert/remove cycles.
I would be much more worried about sideways knocks to the plug while it is in the phone, e.g. from being dropped on a desk. The springs on the plug will make no difference to that.

BTW, older USB connectors have equivalent springs in the socket, but they can fail eventually, and its much easier to replace a cable.