Biologically, 'grounding' is utter bullshit. Psychologically, it is a powerful tool and can really help with certain common difficult mental ailments.
For example, a common exercise to alleviate anxiety (especially when associated with depression) is to focus on the present, on the sensorium, and simply observe; and to avoid conscious thinking. It shares many aspects with meditation, obviously.
'Grounding' can be taken as a wider application, combining a psychological narrative to help mentally 'connect' one to their surroundings, with associated mythology that helps shift the overall mental state to a more productive, calm, 'grounded' (as in 'externally supported, not alone'), positive one. It is pure psychology, but uses scents and tactile sensorium to bypass the conscious part of the human mind. In my opinion, it belongs to the same class of 'tricks' as optical illusions and sleight of hand, except with very useful results.
It is sad, but absolutely expected, to see people take the core idea and run hog wild with it. It is what humans always do, when they think they found something useful.