In my work we've been struggling through some join issues lately. Before you jump into asking "well what are you really trying to do?" ... this question is only about identifying if Insights has changed how it handles joins, and not about troubleshooting the data
One thing we noticed is that we cannot seem to perfectly re-create the structure of a joined layer we created in Insights in November, now in late December. We are not sure if how Insights builds a joined layer has changed.
In both cases we created a relationship in Insights between two layers, using a full join, based on location.
In particular, the output of the original join we did in November only included the two joined layers.

However, now we are trying to re-create the same sort of join with newer data, and finding that the output from Insights includes a third item ... a "table" of the join.

My main question is simply - has there been a change in how Insights does these joins, or are we somehow not doing the same thing we thought we did before? I feel fairly confident we are doing the same sort of relationship building and sharing we did before, because we can't see any other options in Insights that give us this output. But :Shrug: we aren't totally sure. Does it somehow matter what data is being joined? We are working with example data ... the example data from November was more rudimentary. The new example data has more detail. Does that explain this "table" showing up in the join result? Ultimately the reason we are using Insights here is because it provides the option to do a full join, that we do not see as an option elsewhere in AGO... and we are trying to avoid using desktop GIS tools (Pro, Map, etc.).
Thanks for any info!