In my experience Gardai are very slow to act on this kind of infringement, and yes, I've been stopped and warned for doing something stupid in the past. Either they got an over-zealous Garda (who was still absolutely within their right to penalise an infringement under the law). or maybe the Garda who witnessed the manoeuvre actually considered it sufficiently dangerous to go through the paperwork involved.
There is limited information in the opening post, so we are not in a position to judge the degree of danger. The local authority in their assessment have indicated that overtaking must be completed prior to the start of the continuous line to be safe, perhaps due to an upcoming bend, dip, etc.. They have trained specialists who decide these matters. Without evidence to the contrary, I can't see how anyone could conclude the move was safe going on the details provided.