When collecting rocks with the rover, you should be able to directly grab small rocks that fit in the container without using the drill or jackhammer first. These often contain hardly any material. This would make more sense and would speed up collection since the crusher will shred them anyway.
The rover's drill shouldn't destroy the rock fragments, just break them apart. Because the control is more difficult anyway and the use takes much longer than with a jackhammer. Therefore, more yield should be generated with the drill than by hand with the jackhammer.