I think you do not need compass calibration when in EQ mode because plate solving during the polar alignment process already knows where the North is. The compass is still being used in the process, when the app tells you by how many degrees to rotate the telescope left or right, this is a relative measurement so an absolute calibration is not needed.
By the way, I finally got my Dwarf 3 and I am able to answer questions relative to differences between it and the ZWO S50. This is not the right place for comparative reviews and I am not going to do that, but relative to this particular question, I can tell that the SeeStar EQ calibration is better than the Dwarf 3 one - they both work rather well, but in the case of the Dwarf 3 you achieve polar alignment by repeating the whole process multiple times, which is slow. In the SeeStar case you only do it once and then the app helps you interactively to achieve polar alignment by showing you the alignment error in real time, as you make changes. The Dwarf 3 cannot do that.
