If I insert 4 Qwas dogs or 4 Parf dogs into my MFT with two horizontal and two vertical, I can put any of my Woodpecker squares up against the dogs with absolutely no rocking. Woodpecker squares include MFT specific square, framing square, etc. I’ve never altered any of the squares.
All my Woodpecker squares measure out perfectly square to the extent of my ability to measure them.
When I use 2 horizontal dogs and a big Woodpecker square to true my TS55 drop down rail, my cuts are extremely square.
All this indicates the holes in my MFT are very accurate.
As to the rocking you are experiencing, I woud borrow another large trusted square and repeat your rest. Alternately, you could send your Woodpecker square back and have them verify it is accurate.
Hope this helps.