I think you're making a mountain out of a molehill. Whether or not the dealer was technically correct, he is towing the line by avoiding any discussion of tuning the saw and violating federal laws. Some dealers are more strict about this than others, but it's their butt on the line. As far as Echo corporate is concerned, there are no customer adjustments on any of the saws with EPA stickers. Same for other brands, by the way.
Technically he might have been correct depending on interpretation. Some engines are tuned at the factory and then they put the limiter caps on and you could not physically increase the fuel on the high or low adjustments (decrease only). Other engines have the screws completely sealed off, or they put some oddball screw head on them that isn't adjustable with off-the-shelf tools. In both cases, the idea is to prevent customers from making adjustments. You can defeat this either by prying the caps off, or making/buying a tool outside normal channels.
There are some newer saws that have no adjustments at all on the carb. I mean none, zero. These are the ones with an electronic carb. The saws will claim to tune themselves to local atmospheric pressure in realtime, on the fly. Some have a small connector that an authorized dealer can hookup to a diagnostic device, but there are no mechanical adjustments at all.
I've never looked at the carb on my Husky 562XP that has auto tune to see if it has adjustments, but I suspect it has none. A pro saw with no carb adjustments seems like a bad idea, but it's been a great saw over the last 3-4 years and I have never needed to fuss with it.