This is such a divisive way to frame it. But no women aren't effectively working for free until the end of the year. You are not working for free because someone else gets paid more.
This article and the few others i've seen present this as doom and gloom but I think its good news. An 8% gender pay gap is one of the lowest in the world. Judging by the trends it looks like that will be completely closed in a few years as female wage growth is outpacing male.
Its mainly comes down to the average wages in different industries and if we paid teachers a decent wage it could close the gap immediately.
I dont know its a hard problem to solve. Above my paygrade thats for sure.