The "green button" icon used to appear nightly, when WMC started its Guide update. Well, that doesn't happen any longer with EPG123 installed as the whole WMC Guide functionality is "declined" and not installed when configuring WMC. And that's how things have worked for years.
All of a sudden, starting yesterday, I now see the "green button" at no predictable time, and it remains present and visible also for an unpredictable amount of time (although it's typically long).
For example, yesterday afternoon I noticed it. Nothing was recording. The context menu suggested that an update of some kind was going on, since the "cancel update" choice was not grayed-out.

And right now, middle of the night, there happens to be a recording going on. And there's the "green button" again, this time it is the "update data now" choice which is not grayed out.

So what's going on?