This summary has several inaccuracies; the original University of Cologne press release makes a lot more sense.

Their central point is based on the Motor Theory of Speech Perception. This is not a widely-held view within the field.

Besides that, I have to question the validity of treating sugar cubes as a control group; I'd also wonder whether an ad for butter might be affected differently by eating popcorn than an ad for just about anything else. The sample size was quite small. All-in-all, I'm not convinced when The Guardian claims cinemas are likely to give up their main source of revenue.