Great question and suggestion! Let's review p. 24 of the rulebook:
The difference between the two ranks is the number of casualties the loser takes. If hand ranks are tied, both players take one casualty. Both players may also be required to take additional casualties through the use of card effects. A player takes casualties by discarding or acing dudes in their posse: discarding a dude covers one casualty (they were either wounded or run out of town, but live to fight another day), and acing a dude covers two casualties (the dude was shot dead). Any goods with the Sidekick keyword attached to a dude in the posse can also be discarded to cover one casualty. See also Harrowed dudes, in the Rules Compendium, for more options.
Starting with the loser of the round (or the leader if there was no loser), each player must ace or discard enough dudes in their posse to match their casualties. They must match the exact number of casualties if able—they may not voluntarily take more or less casualties than required. Each player (in the order described above) first assigns their casualties by announcing which of their dudes and Sidekicks will be aced or discarded in sequential order. Next, that player takes their casualties, resolving each one at a time in the selected order until they have met their required casualties (so if a card effect forces a dude to be selected as the first casualty, they must also be resolved first). In the event that a player takes zero casualties during a round, they still assign and take casualties. In this case, the player will assign zero casualties, then take zero casualties. This is important, as there may be card effects that interact with either assigning or taking casualties. If a card effect ever forces you to take casualties separately from the difference in hand ranks, there will still be the process of assigning and taking those casualties. Note that even if the loser must ace or discard all dudes in their posse, the winner must still take all their casualties. Remember that while aced dudes go to your Boot Hill, their attached cards are discarded instead.
We recognize the need for clarification and as such in the next update will include language similar to the following:
Cards that will increase casualties affect the number of casualties a player takes when they reach the "takin yer lumps" step and they do NOT make an immediate casualty occur.
We hope this will provide clarity to this concern and thank you for bringing it to our attention