Do all light meters read for middle grey?

Some reading on exposure and Digital

"It turns out that camera meters are not actually calibrated to make whatever they see medium gray. Instead, they are calibrated, according to ANSI standards, to make whatever they see slightly darker than medium gray by about half a stop. Ansel Adams supposedly argued to have this changed but was unsuccessful."

This actual article, is more about Nikon cameras rather than exposure in particular, but in typical internet fashion this leads me to other worthwhile reading.

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