Ok, now I see why I thought this was not working at all: Typicly I copy a step into an empty space, and that does NOT work. But yes, In the way you describe, you can copy one step to an already active step, but isn´t that a bit amputated?
And further: Now that I found out how it is intended to work, I thought: Ok, an advantage of using the SEL button here could be that you easily can select several steps across tracks, and then copy them, but no, it is only possible to copy one step at a time.
So my thought is:
Either fix the current behavior so you can paste into non-active steps AND add multistep copy. Or: Make step copy work without the use of SEL (and forget multistep copy).