Ask the manufacturer how they measure the bending strength. Do they use a 4 point bending fixture? How do they calculate the strength value? Most importantly, what is the surface quality of the glass.

Glass is a brittle material and its strength is highly dependent on the surface quality. The smoother the surface, the higher the strength. If the surface is roughened or etched so that adhesive can bond to it properly, the strength is greatly reduced.  A plate with holes in it creates a stress concentration. How are the holes created?  Microscopic examination of the edge of the holes will reveal small cracks or scratches that will lower the strength of the plate.