FWIW, never heard of MaP flushing or toilet ratings...
However when we were looking at this home we now live in to buy, (it was a new model/spec home for the builder) our real estate agent made a minor derogatory comment about the Gerber toilets. I said as long as they work for a while, no problem--toilets are an easy change.
Four years later, no issues with any of them, they all flush well regardless. Don't know the ratings. I would not imagine they were costly since builders try to thrift things, not spend money on costly toilets that may have a higher rating, but still look like--well, toilets! If they ever spend "extra" money it's on things that people can see and go "Wow" on. Crown molding, two colors of paint, stainless appliances. Toilets? No.