if u are skeptical then pay more lo, he took the risk, buy 1, tested ok can liao..
I am just wondering what test is being done. Most electronics are built to withstand certain deviation and short term use of some non standard accessories may be feasible. However, long term wise we are all not sure.
If you followed Benson Leung from Google, he did testing with a USB sniffer like the third party one in the link below. In another word, any person can test without the technical knowledge and know how, but how reliable the test outcome and whether there is a possibility of damage few months after using the accessory is anyone's guess if it is testing by using it without scientific way.
I am not discrediting others who buy, use and feedback.
http://plugable.com/products/usbc-tkey/
As for the Seller doing Choetech cables, first the manufacturer have not state officially that the cables are within spec (e.g. With the 56K resistor etc) while their other cables are stated with official spec for USB PD. We all know how great advertisements can be. Marketing people does not know technical stuff in depth and they may just put wrong information on advertising.