Hi Paul,
I could not access the links but thank you for stating the Group Layer action in the Map Viewer beta. I was able to reproduce the problems you both were seeing by doing the same.
It seems like the Filter widget did work (used a connected List widget and it filtered out the results), but the Map itself has some rendering issues for the changed data source (and also the selection does not work) - I assume you were both talking about what you saw with the Map, correct?
In the meantime, we will take a further look at it.
Best,
Tonghui