Yes it is a form of black and white point adjustment the idea being if there both set correctly the other colours should be right hence the colour correction link.
The way this is different is it defines the black and white points as points that still have detail thats why it is called "meaningful black" and ties in with the zone system.
It can be performed manualy and the script just simplifies it and automates the task but here are some links from episodes of meet the gimp that talk about the process and the script and what its trying to achieve, some episodes are a bit long but I found them interesting
.... but it is another way of setting black and white points all be it differently.
Meet the GIMP » Blog Archive » Episode 056: Meaningful Black and Ironing Aprons
Meet the GIMP » Blog Archive » Episode 058: White is Grey – and Black too!
Hope you find it interesting
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