It has been said in earlier posts that sanchin kata contained no bunkai. To expand further on "no bunkai".... but, it does contain (principles of movement) that can be inserted into bunkai throughout the kata... Case in point, there is an old Chinese saying, "when the hands wage war above, the legs are in turn waging war below". Every step forward is a potential sweep or a strike to the shin as a disruptive move. This is why the stepping forward move in sanchin does so in an arc inward as it moves across to your stance. There are many principles of movement never explained because it would interfere with the base teachings of sanchin which are, the transfer of power through (structure...movement...breath) and is enough to think about at that time.
Anyone that has ever trained in an Okinawan dojo, in Okinawa...... knows that questions are not allowed, just do and don't talk....Old school