INSERT INTO selected columns creates new column from JOIN
Argh.. Stupidity reigns supreme. In response to Aaron's comment (which deserved an up-vote for stating the obviously overlooked), I traced back through the nested stored procedures. Turns out there was an ALTER TABLE that was adding the columns with NULL values from some old legacy script that was an attempt at trying to do what the INSERT INTO was able to accomplish all along.

@Aaron, thanks for stating the obvious which lead me to check the code path to this point.