there is no definition that you can attach to "class", that makes it correct for this usage, unless you want to change what the word means. Heres a good quote [1]:
> an expression /re/ can be used to specify a range of lines (matching the pattern), which can be combined with other commands
So the command contains a regex, but its not a regex itself, and its not a class of regex. Sorry, but you don't get to just say "well that's not my definition", and get out of it. Sometimes, you're just objectively wrong. It would be like saying you "donated" something, when you really "pledged" it.