You don't exaggerate yields, you just publish the best one you get out of a dozen attempts. Chemistry is messy.
Compare the yields in a typical JACS (or any high end journal) paper versus those in OrgSyn and I think it's pretty clear that yields in many papers are more than exaggerated. It's a single untraceable number and the outcome of your PhD depends on it - the incentive is very clear. Leave a bit of DCM in, weigh, high vac to get rid of the singlet at 5.30ppm and no one's any the wiser...
That, in science, is called "lying".
Either you publish the range of results, the average plus standard deviation or average plus standard deviation of a subset with the exclusion criteria and exclusion range. Picking a result is a lie, plain and simple, and messiness is not an excuse.