Here is another Eric Schmidt quote on radars:
Eric Schmidt: However, our report says that it's really important for us to find a way to maintain two generations of semiconductor leadership ahead of China. Now, the history here is important. In the 1980s, we created a group called SEMATECH. We had a bunch of semiconductor manufacturing in America. Eventually that all moved to East Asia, primarily Singapore, and then South Korea and now Taiwan through TSMC. The most important chips are made in Samsung and TSMC, South Korea, and Taiwan. China has had over 30 years to plan to try to catch up. It's really difficult.
Eric Schmidt: We don't want them to catch up. We want to stay ahead. We call for all sorts of techniques to try to make sure that we rebuild a domestic semiconductor and semiconductor manufacturing facility within the United States. This is important, by the way, for our commercial industry as well as for national security for obvious reasons. By the way, chips, I'm not just referring to CPU chips, there's a whole new generation, I'll give you an example, of sensor chips that sense things. It's really important that those be built in America.
https://www.hoover.org/research/pacific-century-eric-schmidt...
Sensitive radar sensors plus machine learning may or may not be enough to extract people's inner speech - and would surely be a risk to "national security".
If someone like Schmidt is so afraid of this being available for other countries, it is safer to assume it is feasible and he knows it - given he has also been saying people will be able to clone themselves as virtual assistants that will outlive them.
Albeit, feasible or not, researching and demonstrating it is whole more difficult when a billionaire is "calling on all sorts of techniques" to assure their monopoly.