As we know that few games actually play to 11+ level, I would argue that any ability past 10th isn't part of the "core class", its part of the "epic version" of the class that only a handful of tables will experience. (heck even levels 9 and 10 are pretty rare for a lot of tables).Relentless Rage has a short rest mechanic in it.
So if a class doesn't get short rest mechanics until 11+, I would argue the class identify does not include SR.