Dealer's come in all sizes and shapes, most are generally knowledgeable, some are very knowledgeable, and some may have just joined K and have not completed all of their training, so limited knowledge
When possible, you should try to use a local dealer, not only to support local business, but to also have someone that can send techs to help with problems. Some dealers are what I refer to as "sell and forget" dealers, but these folks are slowly being weeded out.
K does not require Support to go through the dealer, BUT it is the preferred method because it may result in a much faster fix because many problems can be solved by the dealer, versus starting and working a "Case" with K Support.
I don't know the percentage, but there are too many owners out there that do not have a dealer, but they will still be Supported on any in-warranty issues.