Well in this case it depends on their conduct and ability to do so which isn't solely algorithmically determined as is evidenced by the numerous other centralized stakers that have collapsed, taking the money with them. I'm under the impression Kraken can take the crypto and do what they want with it, so long as they keep their promise to you. That's exactly what a security is.

I think the distinction is that with a bank's savings account, you are guaranteed your money back, they have all sorts of rules that apply to banks to make that true. Obviously crypto folks don't want it characterized as such an account as that would result in even more onerous limitations. In a decentralized system, there is no person in the way, whose conduct can change whether or not you get the money.