70% efficiency requires 43% more power, your article says “47% more power than a cable” at the top which is a little worse but wait “In general, the propped-up design helped align the coils without much fiddling, but it still used an average of 19.8 Wh, or 39% more power, to charge the phone than cables.” that’s better than 70% efficiency. So ~70% efficiency is spot on.

Wireless charging can do 15+W depending on the phone.

As to the scare quote about 3.5 Billion phones, the charger they mentioned consumes 0.25W when the phone isn’t attached or 6Wh per day that’s the same energy it wastes charging a battery 12Wh per day. You can find many wired wall chargers that waste more than 0.5W when the phone isn’t charging so using one would actually take more energy than using that wireless charger for a single phone.