I work for a Honda dealer and can tell you there is no clear statement from American Honda not to use synthetic. As mentioned earlier, the owners manual states you can use synthetic oil, as long as it meets the other requirements.

Now, in the parts guys defense what he may be confusing or referring to is that American Honda makes it VERY CLEAR to it's dealer body that it does not want them to recommend services that are not in the maintainence guide, nor services such as "engine oil flush," "transmission cleaning systems," etc, etc. Some dealers head these warnings, some do not...

What the Parts counter guy may be trying to communicate, or what he may understand is a statement in regards to "not recommending synthetic oil unessessarily, ie. as an expensive upsell in the service department." I can just picture it now, "Mr customer, not only can you get your L,O,F done every 3 months or 3,000 miles here, but instead of $25 for an oil change, you can pay us $50 for the addtional protection offered by our synthetic oil - it's far superior to traditional motor oil in so many ways!"

That's just my guess and obviously purely speculation but who knows...