It's not a loss of down, it's an exception that allows succeeding spot enforcement. The important thing about this not being the same as a loss of down is that if a team had 3rd and a country mile and decided to try a surprise punt to flip the field, then a loss of down foul would make it 4th down and K would still have the ball. That's not the case here. True, the exception does take away the ability to replay the down, but that's because it allows succeeding spot enforcement, not because it carries a loss of down.