The point is not that it's a particular strain. The point is that most people can't just sit back and let their mind go - to maintain focus requires concentration, and concentration is not "free" - it takes energy. It may feel energising - especially after you're done -, the same way exercise does, but people who think that meditation is "just relaxation" usually have no idea what is involved.
As for the "sprinkle of woo", some meditation practices comes with buckets of foo, while some are entirely woo free.