Yes, the GM standard instruments are more basic than the instrument library Cubasis provides (e.g. GM only has 1 drum kit).
So, for instance, you export a file containing an Electro Kit track → turns into the GM Standard kit → reimport → Cubasis’ Studio kit is the closest match to the GM Standard kit.
On a related note, when exporting to MIDI, the maximum pitch bend range is reduced to 2 semitones.