Never had any issues with mine, even well heeled over and in very rolly
anchorages. The sitting position places the targets very close. So no... no problem.
A bigger question or issue might be to ensure you have adequate hand-holds in the
head to make sure you can hold yourself in place in rough seas. But this is true of all
toilet types.
In shore, if you're heeling so far that it ever does become a challenge, then you have far bigger problems to deal with.