So I looked at the timer itself.
The definition is:
```
[Timer]
OnCalendar=Sun, 02:00
Persistent=yes
```
Right, now it's obvious, 02:00 didn't happen this last Sunday. 01:59:59 -> 03:00:00.
So... yeah, I don't know what I expected but I didn't really expect it to skip it. This isn't a complaint or a bug. It's just another realization of why #DST is terrible.