Quoting from the most recent rules available right now
G33 BOULDERS may only be introduced to the FIELD
A. during TELEOP,
B. by a DRIVER or HUMAN PLAYER, and
C. through one of the holes in the HUMAN PLAYER STATION.
Violation: FOUL per BOULDER
G34 No more than six (6) BOULDERS may remain in a CASTLE at any time. If the BOULDER count ever exceeds six (6), excess BOULDERS must be introduced to the FIELD immediately.
Violation: FOUL per excess BOULDER
By this the rules would imply that there is a forced foul should 2 robots get one boulder in the castle each and a 3rd robot manages (in some amazing way) to get a 2 boulder auton. In this situation it would be during the “at any time” of the 6 boulder limit causing a foul, if you tried to say that putting a ball onto the field was the way to avoid this you are unable to put balls onto the field during Auton. I suspect this would never be an issue but FIRST GDC should probably change the wording of “at any time” to during Teleop, and add in some clause for immediately following Auton reducing the Boulder count in a castle to no more than six (6).