This is a solved problem but I was wondering if anyone had any insight
into what the source of this issue was.

We were seeing modify events come through on an unassociated object, and
as expected query for the attributes in the filter, but when the Synthetic
Add was generated the resulting document was missing certain attributes.
We scratched our head for a while then we looked at the XML of the filter,
and found that the attributes in question had an XML attribute setting of
from-all-classes=”true”. Where does this come from? What
should we not have clicked?