Style Name 'Italic'

is it necessary to have the word ‘Italic’ in the style name to access it with Cmd-I e.g. in TextEdit or Pages?
Let’s say (suppositious) I have a symbol font ‘Hexe’ and two font styles ‘Haensel’ for Regular and ‘Gretel’ for Italic. ‘Gretel’ doesn’t work with Cmd-I, though ‘Gretel Italic’ does.

The OS X type engine applies some undocumented heuristics to see if something is italic or not. To my knowledge, the name and the italic angle are involved.