Any append-only data-structure will have data that was true (when it was written), but has become false/obsolete/garbage at a later time. This is unavoidable.

Any append-only data-structure will have data that was true (when it was written), but has become false/obsolete/garbage at a later time. This is unavoidable. I'm not saying that we write needless garbage to the logs or filesystem or whatever. I'm saying that the amount of garbage in your stream that you leave behind aids in later steps of (static) wear-leveling. So therefore, its not a big deal. You're going to be making plenty of this (initially true data, but later garbage data) as files get updated, moved around filesystems, or whatnot. "Garbage" in this sense is perhaps the wrong word. Its more like "Obsolete data", or "outdated data".