Those Apple mirrors (err, thunderbolt displays) were definitely not close to color accurate. The macbooks are okay I guess?
When I worked at a major printing company, they were not using Macs because people would THINK they were color accurate when they were very much not, and we had a bunch of calibrated Dell monitors around specifically for that purpose.
So definitely more of an urban legend than anything. Apple displays are reasonable, they're decent IPS panels, but they're middle of the road if anything.