if you've ever actually done the math, you will realize that the numbers come out evenly. each party would get a fraction of an extra seat. with 11 parties expected to exceed the "threshold", those fractions would add up to approximately 6 seats (an average of .5 seats per party), the equivalent of an entire other party, or more than the difference between the winning and losing parties.
agreements between parties, such that left-wing, or religious parties, can pool their excess votes, actually helps to ensure that the knesset better reflects the real intentions of the electorate. (in most cases; the united arab list may be the exception.)