This wasn't enforced from outside. It's the organisers who agreed: yup, that's not what we want to do (https://twitter.com/nmsanchez/status/870811022306574336)
Stop for a moment, think of how you'd organise a conference. Is it different? Will people find it inviting? Will they find it interesting? Go ahead, and organise it! Every community and group of organisers can shape the events they create the way they want to. ElectronConf organisers made such choice.
For the people that worry so much about speakers... I haven't done many talks (2 bigger events), but if I heard my talk was delayed so the conference can be rebalanced / less of a white sausage party, I'd be glad. Others may not share that opinion. But don't assume everybody will.
Edit: Yes, there are better and worse ways to go about it. Realising too late and reverting the original list was not the best. Reaching out to / inviting diverse groups rather than fixing balance later would be better. Hope they learned and will do it better next year. Organisers which care about it from the beginning somehow manage to get a decent m/f split - both in the audience and in the speakers. (see linux.conf for a good example)
Edit2: A few people assume that talks will be dropped / replaced as a result. I don't know what the organisers are planning, but there's always an option of adding another room/stream. Until any talks are confirmed as dropped, this is just baseless speculation.