It's likely that the "Tech" who did the test is not a watchmaker but only somebody who has minimal training on a "dry tester".
These testers are a chamber with a dial indicator touching the top of the crystal. As it is pressurized the theory is that if the case is leaking it will let air inside the case, and the case will expand slightly, indicated by the dial indicator. A sticker on the back can give a false movement to the dial indicator.
I would find someplace with a real watchmaker and proper tester that actually shows where the case is leaking from when it fails..
