Head replacement for a misfire (code 304)?

Our 2012 JK has 100,500 miles when check engine light came on. Code 304, replaced spark plugs, all, and coil on number 4. Code comes back. It's now at the dealer. Head replacement. My question is; Why are these heads being replaced for a misfire situation? Dealer hasn't answered the why. I was a ASE Cert Master, left the trade as I was becoming very allergic to all the chemicals that we used, maybe causing my bout with Leukemia. So I looking for a reason for replacement. 80's Audis were breaking exhaust manifold bolts and they were covering head replacement for that. It was very difficult to extract the broken studs.

 

Just like @chris4x4 mentioned about past TSBs. As you know some TSBs are not common knowledge. I was fortunate last month a TSB existed for my 2011 Outback AT. The TSB centered on torque converter failure once the car approaches 100k. No recall, no notices until years later as more people complain. Outback is fixed but I'm spreading the word on that TSB.

 

Welcome to the forum skiteach.
Awesome info posted above that I was not aware of. So i picked up some knowledge also. Thanks guys.

 

We purchased the JK used, also an extended warranty. Radiator and heater core were replaced, due to lack of heat. We received a Warranty Extension, for the left cylinder head, from FCG, or what ever they are calling themselves this month. So one head is covered. Still waiting to see what entire process is! Even the internet has very little info on this! I worked at a Dodge Dealer, for a short time in 1988. Chrysler had a few problems with valve guides around the time I left the trade. Now I bang nails and butcher long lengths of wood. Finish Carpentry is easier on the body!