They might have in the slight time frame between high school graduation and marriage (~25 years for Chinese women). Before they have not much say because their fathers are the boss. Afterwards they have husbands who don't do anything but work and sleep (and maybe care for their mistresses). It's true that in that short slice of time their power over each single men who wants them is nearly unlimited. But would you trade your whole life for 5 years of power over guys you don't care about?
And it's not really true that they have power in a global sense, it's only in each of these 1-on-1 encounters with potential marriage partners. On the global scale requirements like beauty and social standards are higher and the push to marriage is also stronger than for men.
So this "has backfired on men" should be read as "has decreased the huge advantage of men to become only a big advantage for men".