"That's because index funds typically rebalance monthly."
Please reread. The issue was about the immediate impact of a Nasdaq entry: "A Nasdaq entry would allow for investment by institutions who would realize that inclusion in the Russell 2000 would provide a kicker when it occurred in June."
"it would take at least a month to get a real pps improvement" That's true, but it wasn't the subject. That's because index funds typically rebalance monthly.