The difference is two-fold: actively planting a fake story means that first, the espionage is fake and thus no real intelligence can be gathered, so the only benefit is the hypothetical respect you suggested; second, the story will definitely get out, thus the potential for the negative effect is innately 100%. However, as a real intelligence operation the cost/benefit analysis is inverted, because there is a real, tangible benefit to extracting possibly sensitive commercial and national security information. And while an eventual discovery is always a possibility, it seems care was taken to ensure it would only be a small possibility, and that in any case it would be in the future, hopefully after a large amount of useful data is extracted.

So in the planted story hypothesis, there is certainty of negative outcomes with only the potential for positive outcomes, and those only intangible, while in the this-is-real hypothesis, there is near certainty of some tangible benefit with good probability of significant tangible benefit, with only a potential, distant, deniable risk of negative outcome.