Well the real question is when was it changed? Before or after Kunark was released?
And if it was after, did the Kunark giants also see invis?
To partially answer my own question, Giants in the Frontier Mountains usually saw through invis according to a post made in May of 2002:
http://everquest.allakhazam.com/db/zones.html?zstrat=83
Not exactly the best source and doesn't necessarily pertain to current giants but I haven't searched that much yet.