Club Nintendo rewards don't register if purchased on Wii U while in Wii mode

For years now players have been able to accumulate Club Nintendo coins by registering their Nintendo products and taking surveys. These points can be used to grab rewards like games and swag. However, a tipster at NintendoLife recently discovered that games purchased on the Wii U while in Wii mode don't net any earnings, even though the same games purchased on the regular old Wii do.

Why is this? Nintendo hasn't said, but it seems to be aware of the problem as the Club Nintendo FAQ noted, "Due to certain system constraints, Club Nintendo accounts cannot be linked to the Wii Shop on the Wii U. Games downloaded through the Wii Shop on the Wii U (in Wii mode) do not qualify for surveys or Coins."

What are these system constraints and what is Nintendo doing about them? We've followed up with the Kyoto-based company and will update as we hear back.