There are 2 components to delay of game - one, there is no play at all, so no result, good or bad, counts, and two, the offending team gets a five-yard penalty. It's inaccurate to say it can't be declined - it's more accurate to say that the play was aborted when the penalty was called, so nothing actually happened.
In the case of the punting situation, the punting team isn't trying to run a play, so the first part of it doesn't matter.