Not sure why Meta called EMG as sEMG, this just going to mess up search and confuse people.
There are many useful surface electromagnetic (EM) waves for physiological signal detection, for examples ECG, EMG, EEG, and together they are referred to ExG with different magnitudes ranges and characteristics. But people don't refer to them with s initial sECG, sEMG or sEEG because by their very definitions they are belong to surface EM waves category.
The first sentence of the article explains:
> Surface electromyography (sEMG)
EMG[0] require a needle in the muscle, sEMG is an improvement.
[0]: https://www.mayoclinic.org/tests-procedures/emg/about/pac-20...
URL should probably be: https://www.meta.com/blog/quest/surface-emg-wrist-white-pape... (without the locale)