The Configuration / Puppet Classes page shows all available classes and their usage count (in the "Hosts" column), but this count as far as I can tell only includes hosts where the classes are explicitly included, it does not include hosts which inherit the classes by being part of a Host Group where the classes have been assigned.

First of all this is misleading, and makes the usage count potentially useless.

Then it also causes inconsistencies when browsing the GUI: for example you can have a class listed as being used in 0 (zero) hosts, but if you click on the zero you are brought to a page where one or more hosts actually using that class are listed, because they inherit it from the group.