A number of subclasses, like the barbarian and beserker for example, have thief abilities they can use when lightly armoured or unarmoured. Thieves, however, can use those abilities wearing medium armor with a reduction in success chance.

Is that an intentional difference or an artifact from older rules? I can't see making that distinction except to preserve a bit of niche protection. That makes sense, but I wanted to double check.

Thanks.