Bees wax up parts of the QX but leave enough open to get through. In winter you will find more waxing, especially around the center, bit of a self made hive mat, but is removed by the bees in spring.
We hardly ever scrape a QX, unnecessary work and risk of damaging bars. When you remove the QX put it back the in the same position so as the burr wax is in the same position.
Qx's that are removed from deadouts or for what ever reason are cleaned in winter by dipping in hot water.
Michael is right, if you leave the right distance from the top of the frame to the bars of the QX then the bees use it for travelling space and so don't wax it up as much.
Even though the Chinese QX's are steel bound, if you put them cross/supporting bars down you will get about the right space. Our frames are about 1/8" below the top of the super.
I am with Honey Pump, an essential of efficient part of bee keeping.