@3perf
The ISO / ANSI standardizations are probably as well the reason, why you aren't getting the same numbers the manufactures propagate. As you are not using the distinctive measurement standards as they are defined. In the end, these numbers are only meant to have the possibility of a basic comparison between different devices, not exactly a quality aspect. It is kind like the PS/kw for cars.

Since the switch from conventional lights to laser and LED sources, some manufactures tend to push the power of their devices above the advertised Lumens, to compensate the loss of brightness (aging) over the much longer live expectancy (20 000 hours fixed light source vs. 2000 hours changeable conventional bulbs).