Mate, focus (and would you please avoid shoving advice and links when not openly asked?!): 90 percent efficiency claim is directly in the OP.

The number can even be confirmed at the press release by Porsche (which boldly claims charging efficiency to be "over 90 percent").

Focus and keep the number in your mind (the number found BOTH in the OP and confirmed at the Porsce's press release) while trying to explain where the losses do take place.

I totally understand, that losses do happen when the electricity is converted first to DC and then back to high freq.AC and during the inductive charging itself.

This is expected and is a convenience tax of sorts (getting rid of cables and plugs) and yet, it's less efficient than plugging directly. Once again, only 90℅ efficient.

I don't have the crayons to explain it to you any simpler 8)