Perennial Walla Walla onion?

I'm not sure really where to post this on here but I've got an odd thing happening with one of my "Walla Walla" onions. This is growing from the flower head of what I thought was a Walla Walla onion. I bought sets of Walla Walla onions last year, harvested them, then some got nibbled on by a rat in storage so I replanted them. Two things I wasn't expecting: 1 when they started to grow, the bulb divided. 2 the flower head seems to be developing bulblets. Is this just something common to Walla Wallas that I haven't been able to find anywhere online? Or is it just not a Walla Walla?

This is where I originally planted the onion bulb. You can see the old stalks where it originally split into 3 bulbs (had one that split into 5) which then rotted while producing flower heads, and now it seems to be producing 2 more onion bulbs.