When Tadayuki Satoh (judo and aikido) visited our dojo, he mentioned the use of "inner movement of the waist" to perform a sumi otoshi. You cannot say in Tomiki Aikido the emphasis is on body mechanics , other elements like "inner movement" makes a technique working in a randori enviroment. Using only inner movement will not work, but good body mechanics (basics) and inner body movement can create a succesfull technique.