The two mentioned in the article met the FDA definition of remission. It doesn’t say, how many improved in general. This is important specifically since the sample size of the trial is small.
Who says it won't last? Most depressions actually do get better by themselves.
How do you think humanity has survived so far?
(Most, but not all. And even if it eventually gets better without meds, there was still a lot of suffering.)
Empirically, most clinical depressions get better by themselves today.
Similarly, most alcoholics improve by themselves.
(Of course, effective treatment is still useful!)
No clue whether it's the depression itself, or whether that's just a side-effect of something else that's useful.