First of all - the comment made me laugh.
I have personally known people like this. The first one I encountered more than 20 years ago and after we introduced her to cross stitch, she started methodically working her way through every Pat Buckley Moss design. The most time it took her was one month. I admit, she was a high achiever in a set of circumstances where she couldn't work and this was her substitute for working.
But we see them in my LNS. They only work one project at a time. And are very meticulous about choosing their next project. I am not certain they are as obsessive as my friend from years ago, but I suspect they are extremely focused individuals.