Lab Cloud

Is the Lab Cloud stunt file representative of what is generally considered the realm of Human Perceivable Color ?

Not quite.
The Lab cloud is an even dispersion of colors throughout the Lab space. It makes for a handy file for running colors through a profile to get color points that are in a certain gamut.

But if you’re looking for human-perceptible colors, they would be roughly (very roughly) in the gamut of ProphotoRGB.

You can get a good idea of the gamut of human perception if you go to Bruce Lindbloom’s site:
Goto Info and Lab Gamut display

It’s interesting to note that some very saturated greens and yellows in human perception are outside of Lab space.