Spark's "unilateral exit" requires using their API -- which is often down, and in any case, the "unilateral exist", as you probably know, is useless for small amounts, like below 20,000 satoshis (or something like that, not sure the exact number.) And also -- if you have to use their centralized API, why is "unilateral exit" any better than just "log in and withdraw your satoshis"?