alt Hacker NewsI think the effect is actually backwards: there may only be 2 windows instead of 4 but the total amount of time window per year should theoretically go up significantly. The 2 removed reports should make both of those quarters less subject to insider trading and therefore more tradeable.
In companies I've been in, insider trading windows close because there's been a certain amount of time since the last report. So less frequent reports = more time for insider to know things that aren't public yet = more time unable to trade, not less.