I went to the FDA website and found that they didn't get...

I went to the FDA website and found that they didn't get approval on cuff less BP device, but accordingly you need to have a cuff with the device. So it is not cuffless. Mind you they had this announcement for more than 18 months, and since then no clinical study had been done with the device, because (1) their device impractical, (2) inaccurate, and (3) better stick with the conventional accurate cuff BP since you need that anyway with their device.
Typical Israeli companies, good in PR but no content.
Also, of course they don't measure central BP.

Also regarding nature journal. This study ( a year ago) was not independent. Most importantly, if you look at the method, they kept using the cuff with the device, and then compared their device BP as calibrated by a cuff with the same cuff.
It is like comparing with itself.

Funny after cuff calibration, they ask the subjects not to move or do anything that will change their BP. Because if they did, their cuff calibration would not work. A real cuff less BP, will be able to track changes in BP accurately either with no cuff at all or with at least one time cuff calibration that last a whole day at least.

This study didn't prove that. It is a poor scientific study made that seems legit but it definitely don't show any device accuracies in tracking real BP changes. That is the challenge, which they fail to prove.

In addition, this is a weak Journal with very low quality (impact factor) according to international medical and scientific journals rating system.