The 70% efficiency only makes sense for a specified distance, unless their antenna sizes will scale with distance.

No matter what tricks they use, the basic radio path loss equation applies, and it is brutal to transmission at any significant distance unless antennas are huge.

Space based power can use huge antennas - after all, the solar arrays are huge. Plus, the receiving rectennas can be many square kilometers.

That's very different if you are transmitting from a terrestrial source. Basically, you are not going to see significant power transmitted wirelessly. Period.