UL does indeed test the claims of device manufacturers. It is not what they are normally known for, but it is a service UL provides.
With respect to this posting on Batteriser's site, this appears to be a test description that Batteroo provided to UL. Worst of all, the test is specifying this strange test fixture where the batteries are placed in the external battery box, while the GPS is attached to the fixture with the native battery compartment inaccessible. This test fixture seems to be strangely necessary to produce result Batteroo is reporting.
When these GPS devices are tested doing the thunderingly obvious, placing the batteries into the device's battery compartment and measuring the voltage at the device battery terminals, a completely different result is obtained.
Lastly, this "report" excerpt appears to be Photoshopped. The UL logo looks like it was copied off somewhere else, the white background is different that the white background of this "report." If this really was excerpted from the real report, the entire white background would have the same tint.
Oh, and by the way Bob, you spelled "battery" wrong. I'm pretty certain the UL uses spell check.