In the event someone stumbles on this post, according to customer support this is expected behavior in a cross app relationship.If needed, use the work around I provided by creating a mirrored field to the proxy field.
For mine, I took it one step further. The proxy field simply needs to be included on the mirror field, other items can be there. So I made a rich text field, mirrored the proxy field but made it size 1 font, and white (so essentially hidden), then mirrored another useful field. Works out pretty nice. No clue why it works but, there it is.