They are different than multiplier onions and elephant garlic. It is a bit hard to find info on them and if there are different varieties.
https://living-mudflower.blogspot.com/2013/09/comparing-perennial-leeks-with-regular.html
I like perennial alliums, I have I'itoi onions, walking/egyptian onions, welsh onions, chives, elephant garlic, shallots. I want to pick up potato onions.
They will make good sized leeks if given room. You can plant starts and let them mature, then pull up the large ones and take off the small ones and replant. they taste great and are easy to propagate.
I got them from Planting Justice in Oakland, CA.