The anode is magnesium and it was passivated. That is a wild-card situation where the anode appears to go to sleep. If it’s asleep, it may not be doing any protecting. On the other hand, your tank is 11 years old and hasn’t rusted out.
That’s why I say wild-card.
I’m going to suggest that you get a new anode, preferably from me;), and install it and check it in a year. When that time comes, send a picture of it and I’ll tell you where I think things are going.