After the lock screen, the graphs are empty

Hello, I installed this extension on Ubuntu 18.04 (bionic beaver) upgraded from 16.04 using "do-release-update -d" in order to replace the "indicator-multiload" I used on 16.04.

For that purpose it works ok, and might even be a bit more polished. However, one thing I noticed is that "indicator-multiload" keeps on "graphing" even when the session is locked (after inactivity, or Super-L). This shell extension does not: when you "log in" again from the lock screen, all graphing is reset.

It is just a sight annoyance from the (for me) expected behaviour of continued graphing. This might be by design, or even impossible using gnome-shell-extensions. I don't know.

The question would thus be: Is the described behaviour normal and expected. If not, should I file it as a bug?