Why did UL 62368 not use UL 101 method ("e" is always open) to measure touch current? what's the background?
UL 62368-1 is harmonized with IEC 62368-1. As an electronic standard it utilizes the leading information on assessment of electric shock. As part of this it follows the testing protocol of IEC 60990, Methods of measurement of touch current and protective conductor current.
62368-1 also considers risk to a person under normal, abnormal and single fault conditions. This is a basic principal within the Standard. In line with this philosophy, IEC 60990 considers the various faults possible based on power distribution system (single phase, 3 phase Delta, etc.) and power systems e.g. TN, TT, etc.
An aid is available to all users of IEC 62368-1, it is the technical report IEC TR 62368-2, Explanatory information related to IEC 62368-1:2018. Within this document it explains how hazard based engineering was followed and resulted in the development of the requirements. The document can be purchased through your regular standard acquisition channels.
In addition to the rational document, there are a number of technical papers available on the development of IEC 60990 and it’s principles.