If a player deliberately knocks the ball up in order to make an interception by running under it to catch it, he should definitely be penalised. That is not a valid interception technique.Hmmmm I take your point, but given we see it happen in matches all the time at higher levels and refs allow it, it'd be a hard sell. Would basically do away with interceptions. These are exciting to watch when they happen.
If he tries to catch the ball but accidentally knocks on, that is only a scrum offence.