"Metaconcept" (left-BP519) implies "sideless."
Left examples have the keyword "side" on the OEBP.
Right examples have the keyword "sideless" on the OEBP.
"Flipping" doesn't mirror the examples; flipping only switches sides.
Meta Bongard Problems such that if the sides of an example Bongard Problem are switched its sorting may switch vs. meta Bongard Problems that always sort Problems and their flipped versions on the same side.