I think the person at your store was interpreting the above quote to mean that it is now unofficial, which i believe is not the intention. That same paragraph also states that models wielding two clubs are overpowered compared to a model using a shield but no solution is proposed. Using your friend's logic, that weapon combination is unofficial as well, which is just silly!
All i can say is play the scenario; if it feels unbalanced don't play it again, if you don't notice anything wrong with it, forget about that quote and continue playing!
Edited for clarity