Just like any 16" team would get demolished in anything probably C or above in 12".
The games are just so drastically different.
Hitting a 16" ball well is an art form as is playing defense with no glove. No Glove Nationals are also played on fields with no fences so it's not like they could just get a bunch of mashers either.
The speed of the ball in 12" would blow most 16" guys out of the water. Even if the 16" guys could hit it they would get 30-40 put on them easily by most good teams, probably more depending on the HR rules used.