Yep,also what I was wondering about, but so far people's feedback has been positive as far as I can tell, though not always easy to decipher, fx which Youtuber has been greased with these products for promotion alongside having an incentive to profit from affiliate links etc, and who put their own hard-earned money behind it.
A shame, they ditch it, as it can't be cheap to produce such a standard and then just use it, for only +1year, I doubt Micsig will be open about it, if there are issues with the standard, though can also just be cost, and not having to deal with two proprietary Micsic probe interfaces. (SigOfit and UPI)
UPI was promoted as a universal interface, so perhaps it was intended that other vendors would jump on board..