I believe you are correct. I just researched the issue and it appears this is not rare, and has been observed in several models of J frames with frame mounted firing pins. Someone posted a video of this on You Tube in 2009. Theories include spark due to air compression within fp channel providing enough heat to ignite lubricants - kind of dieseling effect? Anyway, several commenters many yrs ago said that S&W was aware & stated it was normal & did not result in abnormal wear or damage to components. In any case, an interesting phenomenon.
Enjoy Cocoa Beach; my parents lived there for many years.