Well, thanks, but: first off this is an older version of the rules, I think you meant to link the newer one which has the addendum that "In addition, all yellow cards expire on completion of the quarter-finals. They are not carried forward to the semi-finals."
However, this is still confusing, because earlier it says that a player will get suspended following any "subsequent odd-numbered caution". Cards getting wiped doesn't mean you can't get two cards and have an "odd-numbered caution" situation in your hands during the two semifinal legs. So unless the count of the cards also gets reset (which isn't explicitly stated), then the rule is still ambiguous.