Ah - sorry - right, now I'm reading it properly! Second coffee kicking in.
So yeah, we had someone else ask why their Solar+Grid was being reset back to Solar only, which is why we decided to keep the AC charging flag enabled at the end of a charge window. This is one of those things we can't solve for everyone, until we have snapshotting of values in place.
For now, the main thing is, WW does leave the AC charging flag to enabled, but sets a window of 00:00-00:00 - which means nothing is currently scheduled after the charge window ends.
Seemed like a better way of doing it.