Fingers crossed for the JNB-SYD leg getting further availability!
Not wanting to rain on your parade at all, just wanting to point out that Finnair hasn't actually started flying the HND-HEL route yet (due to start with the summer schedule in late-March).
I really hope they will start on schedule but I could see them delaying the launch because they do have a daily NRT-HEL flight already that presumably is flying quite empty. They do seem to be reliably running the NRT-HEL flight every day though which is good so they could always reroute on that.
I'm sure in six months everything will be different though and I'm sure that if the border is open for tourists then planes will be full again.