The most recent issue of Marketing casually mentions, in an article on Stella Artois’ branding, that the lager contains “only the four traditional ingredients of beer” — malt, water, hops and maize.
So, it seems that the sneaky campaign from earlier this year has partially achieved its aim. That is, subtly linking the idea that beer has a limited number of traditional ingredients (as per the German purity law) with the four slightly different ingredients found in Stella.
Maize is not, of course, traditionally found in beer, and has only been included by sly brewers in the last century or so to reduce the cost of production and lighten the flavour.