Non-primary dimension and weight

Hi
While configuring the shipping,  we set primary and non-primary dimensions and weights.
The question is - where the non primary dimensions and weights are being used? It seems, that everywhere only the primary measures are used (in product configuration and shipping calculation).  
It seems setting no primary measures are useless, or I miss something?

Shipping provider plugins (e.g. UPS) will use them to convert dimensions if needed.