Nothing wrong with a shadow. I wish my 1800 had a valve system like one. Then I wouldn't have to adjust valves all the time! 
why do you adjust your valves all the time?
do you actually think the metal wears more than 2-3 thousands?
do you think the lock nut gets lose and the adjusting screw turns?
could it be the valve seat is wearing?
my vote; none of the above, its just a ploy for the service people at Honda to get more money out of you.
I have checked mine at every interval that they suggest. the only time they actually needed adjusting was the first time. after that (three times) they havent moved.
hmmm, I wonder if i need to "adjust" them on my truck every 8K?
