I'm not intending to join in this discussion as such and my own view is that depression is a symptom - no more and no less.
What I wanted to say is that I had severe depression for many years after onset which disappeared when my physical symptoms worsened after 12 years. It just occured to me recently (don't know why it took so long) But when I had depression (the symptom) it was actually relieved by bed rest as is my current PEM. I'd go to bed suicidally depressed and after a few hours sleep wake up feeling pretty much over it.
I don't recall ever coming across any discussions of depression relieved by bed rest.
Very interesting. Generally speaking, depression is effectively treated by sleep deprivation. This has a rapid acute but transient antidepressant effect. Perhaps your experience is yet more evidence pointing to depressive symptoms in the context of ME/CFS being caused by different mechanisms than major depression occurring as a standalone illness.