So I got a reply from WGT support that included...
"We have learned that when you are awarded a sponsor pack the items are
added to your inventory, and not when it is actually opened. This means
that the items inside the box have been added to your account, but were
not displayed in front of you."
If I understand correctly what they're saying is that I don't have to open the bonus box to get the contents.
Can anyone verify this, particularly given that I need to kill the game at this point to get past this? It seems to verify I would need to keep an running total of the points on all my items (or at least the SE ones) during play knowing that when this happens at least one of them will have more points than expected. Bit of a PITA but I'm willing to give it a shot. Haven't gotten a bonus box in about 5 days.