Discussion of Same-Round Immunity:

In the zung jung doc, it says:

When the winner wins on discard, if in the same round (starting from and including the winner's previous discarded tile, until before the win) another player has just discarded the same tile as the winning tile, then the discarder will not be "responsible" for having followed with the same discard. If it is the winner who has just discarded the winning tile, then no one will be considered responsible (the three players split the payment equally). Otherwise, the player who first discarded the winning tile in the same round (after the winner's previous discard) will be considered responsible.

It is quite clear. If a player is waiting on a 1-bamboo tile, he/she can always win whenever someone discards one. In zung jung rule, the immunity is not being responsible for discarding, but it is still a win game. In some other rules, he/she can only wins the first tile in the same round; the immunity is he/she can not win on the discard tile.