Calendar identifier inconsistency with CF conventions

[matthewrmshin]

This is raised by a user in a forum. (I have replaced "Cylc" with "Metomi-isodatetime" and removed any irrelevant parts from the original post.)

CF and Metomi-isodatetime have an inconsistent naming conventions for calendars. Metomi-isodatetime uses: 360day, 365day, 366day.

But the CF conventions are: 360_day, 365_day, 366_day (i.e. with underscores).
http://cfconventions.org/Data/cf-conventions/cf-conventions-1.7/cf-conventions.html#calendar

I will now need to do something like cal.replace('day','_day') ... to set the calendar in a consistent way and use it in python apps that use cftime. Is there a good reason for the inconsistency?