Physical interpretation of higher order modes

I’m interested in the physical meaning when a non negligible fraction of the power of the fundamental mode couples to a high order mode from one cell to another (according to the internal S parameters).
On inspection of the mode profile of these higher order modes it seems clear that the modes are non-physical (extend till the simulation boundary).
Since the power is neither transmitted to a guided mode nor reflected, can I assume that these modes represent radiating modes?

Dear @weilenmc

I think what you explained makes sense and is correct. I can’t remember any specific case that violates your explanation, but feel free to share your file a review (just to make sure that your simulation file is set properly).