The animation is in response to what they are holding but is not representative of what's actually happening. Don't forget how old the engine of this game is. They didn't bother to make little changes like this to the game.

This is the best gauge of if it is working.

They will hold two regardless of if the are actually Dual Wielding.

As was noted in a previous post the battle spam can indicate if it is working or not as well.

If your pet class and double attack, when it is dual wielding you can see some rounds where it appears to quad, (a successful Dual Wield check and double attack checks). Keep in mind dual wield hits can be different values, a double attack hit will always mirror the original swings damage.

Really? I've been playing for years and I never knew that..

Is this a pet specific or server specific thing?

If not, it's wrong.

I'd that to test if they really are dual-wielding, give them two different types, i.e. like a sword and a dagger, and see if the log says they are both slashing and piercing.

If that is incorrect sorry, thought i remembered that from a few years ago when I last played on Live.

Also I thought I saw that in my battle spam, but maybe it was just a coincidence