This is not anatomy, it's a construction method. Anatomy is studing bones, muscles, etc.
I think this is the normal approach, to start with gesture.
Why are you shy to ask the original artist? Ask. Start with: "I have a question..."
I don't think an artist will be mean to you about asking questions. Unless he's a jerk, but that doesn't reflect on you, that's his flaw. Worst case scenario, he's busy and won't reply or he'll say he explained already.
Yes, it's a construction method. Probably invented by the artist, which is not surprising - there are a few well-tried ways to start a drawing, but most artist will grow their own. Which means they will have specific tricks and peculiarities that this particular artist likes or develops - these starting doodles are often more like shorthand writing than a formal construction method, marking down key points and movements rather than building something solid.
Occasionally artists may even capitalize on the quirks of their construction doodles. Case in point: Dali's drawings often ARE overblown construction doodles, and he did have unusual quirks like building things from series of ellipses representing the parallels of a cylinder, so it's easy to spot.
This particular artist relies on lines of action to lay the figure in; in this sample sketch you've linked there are two. One follows the balance, from head through the spine curve to the supporting leg and foot. The other provides a dynamic rhyme to it, describing the non-supporting leg and a rhythmic line around the ribcage. A bit unusual, but nothing really outlandish. You can learn something like it if you start with an action line - refer to the methods in "FORCE" book or Blair's "Cartoon Animation".
The way they continue the drawing shows they aren't very good at tracking structure, anatomy or balance, though. That they call it "classical anatomy" doesn't make it any more classical, this artist has a long way to go yet.