The syndrome - with panic attacks etc - is the most severe response. Most people I know who've been to Paris with high or romantic expectations just get scammed, spat on, yelled at or robbed and feel a bit disappointed.
I've been to Paris a few times and when people tell me they want to go there for romantic reasons, I just tell them to go to Bruges instead. The Old Town of Bruges is exactly the way most people seem to imagine Paris: old buildings, reasonably clean, lots of street cafés and horse-drawn carriages.
Even the Eiffel tower looks better from a distance than close-up (mostly because it's really just a massive lump of steel). There are nice corners in Paris but if you haven't actually ever been to Paris before, you'll probably be disappointed by the overall experience.
With 0.0003% of people being affected, I'd argue that this so called "symptom" is hardly a noteworthy phenomenon.