I didn't claim a miraculous explanation; I only said I no longer think these cases are faked. I think "incorruptibles" are a fascinating phenomenon that I can't explain. I believe in miracles, and I think some incorruptibles might be miracles, but I don't really know. There might be other ways that the lifestyle we tend to call "holy" does something to retard decomposition.

However, I don't think your explanation is sufficient because decay usually begins immediately upon death due to the presence of organisms already in the body before death. Sealing the coffin would not prevent such decomposition.