The current description seems to be a bit inconsistent and unclear. It does not reflect the agreement that we had as part of generating CIM17. It also does not align with my understanding of the Redmine issue: CIM Issues #6202: Modeling guide is missing instructions for data type names in attribute names - CIM Joint Issues - UCAIug Issue Tracking System
I think that the current description does not reflect the agreement that was made as part of CIM17. The latest relevant classes was:

My understand of the issue was to update the Modelling Guide to reflect the agreement that was made as part of CIM17. I think it will be a big mistake to go back and forward on the same it..