If they tried to do this with a spacecraft, wouldn't it need constant line of sight from earth with this technique? Seems interesting but pretty impractical for that application, unless I'm reading the text incorrectly.
Avi Loeb described this on ep. 40 of After On [1], it didn't sound entirely unrealistic as he described it. It's around 19 minutes into the interview, I see a sibling links Breakthrough Starshot, in this podcast he describes it on a high level.