What he meant is that if the sulfite level is high in the wine, it will kill off bacteria that make it into the wine either from an intentional addition or from coming out of the barrel wood. That is, sulfites are doing their job. The reason why MLF can occur in the same barrel the next year without adding new bacteria is that it is impossible to thoroughly sanitize the wood of a barrel to kill off bacteria that are hiding in the crevasses inside there.If that were the case, how could you have it naturally occur the next season, without adding new bacteria.
You are technically correct. It mostly prevents folate synthesis, which prevents growth and reproduction, but does not necessarily overtly kill the existing bacteria. Unable to reproduce, and without external inoculation, the bacteria colony eventually experiences senescence and dies off if sulfate levels are kept high.One thing he said, I don’t believe is true; that by adding SO2 you kill the bacteria.