OMG, this is a lot of misleading information. If it were true, why would my Minolta Spotmeter F give me identical readings as my Canon dSLR, when both are aimed at the same 18% grey card and set to the same ISO value?!?!?!
In fact, using my Minolta Autometer Vf in incident mode, its reading agrees with the two reflected light meters mentioned above, too.
Hahahaha....that's almost like saying each DSLR unit has its own metering standard and photographers can't cross reference with one body with another. I am pretty sure if you meter with an EOS 3 with a Canon 1dmarkIII on the same scene, you get the exact same reading.