At least about the yellowish discoloration on the underside of the toilet seat, my boyfriend recently complained quite a bit. I assume that nothing was splashed up from the porcelain during the toilet visit, but rather it is due to the "spitting" of the bowl - which would therefore also (albeit minimal) result in urine residues on the floor.
We have that with our current toilet as well, and it has a rim flush, so I suspect that at least for us it splashes during use. Of course, with enough interest, this could be quite easily checked: pee, check if splashed (wet), flush, check again.