You are right. A few months ago Jawbone UP3 definitely had HRV listed in the heart health features. That's specifically why I was looking to buy it. I guess that's close to impossible with an optical sensor.
Even the standalone optical HRMs (e.g., Scosche RHYTHM+) aren't good enough to do HRV[1] even though their accuracy compares favorably with the chest strap models[2]