Photo Mechanic seems to have made the attempt to track down the IPTC documentation, so the terminology is as consistent as any I have found. However, in my view, even IPTC has not been completely successful in defining a sound data model for metadata -- some very obvious needs, such as the original (often standard) format of a photograph being digitized for preservation, don't seem to be addressed and are left up to the user to co-opt some field intended by IPTC for a different data element. As a result, digital materials from different sources or different operators are likely to be incompatible for purposes of cataloguing and accessibility.
On closer inspection, I was mistaken about how Windows File Explorer uses the metadata fields. The one that File Explorer calls "Title" is in fact the one that Photo Mechanic calls "Description/Caption", which is the one Juicebox calls "Caption". For my purposes, that still turns out to be the key to loading a Juicebox gallery with photos in the desired order. For my usage, the "Caption" contains all the relevant description, and the Juicebox "Title" becomes superfluous.
A certain early innovator in data processing is supposed to have said, "Standards must be a very good thing, seeing that there are so many of them!"