It is great people are discovering that there is a happiness within that is not dependent on getting things or things being a certain way and you can increase and cultivate wholesome states that are outside the sensory world. But the sort of description of so called "jhana" in the article misses it - it points to the feelings generated in the body. They are rather like a boat and its wake... the wake is the feelings but the boat is something else - they are the wholesome states. We don't focus on the feelings, rather keep driving the boat (focusing on our meditation object). Then ... boom... we suddenly hit a river bank and have no idea what happened. It's unmistakable. For instance with metta the boat would be the intention "may I be happy" the feelings are the by-product or wake. Jhana is proper like a boat that suddenly unexpectedly hits the shore... It rocks and blows the mind (and as the mind contains model of the world - it feels like the world shook a bit then froze). A good "geeks guide" is "Mindfulness Bliss and Beyond" written by someone who finished a physics degree at cambridge and spent 9 years with Ajahn Chah.
If we instead mistake something else for "jhana" like some positive feels, we're going to be stuck cultivating a local maxima. It's not to say the practice is wrong, it's actually quite good. It's just not jhana. We should listen to the professional community just like we listen to the professionals of physics in academia, instead of some posts from people on the internet that have done a few 30 day retreats.
But please do not call it jhana and have some humility ... these terms are central to some of the okdest institutions in the world and theres a professional community in the dharmic traditions who literally do this full time all over asia.
If someone wants to hear a competent speaker who has done the necessary time and training at those institutions and is also trained in the conventional university system, someone like Ajahn Brahm (Theoretical Physics Cambridge) Beth Upton (Economics Cambridge) or Shalia Catherine or Sayadaw U Jagara