That's easy. not all bars handle all HD audio encoding. To make matters worse and why I (I'm not CNET) bother with HD audio on bars is that most TVs yell "You shall not pass" audio beyond stereo if the source is HDMI. That really upsets a lot of folk. Samsungs, in fact all the models I've ever seen are always this way. So check your TV to see if it will pass HD audio. It may not matter here.

The thing that saves this bar is that it has 2 HDMI inputs that means you can get HD audio.

https://www.howtogeek.com/304200/whats-the-difference-between-dolby-digital-and-dts-and-should-i-care/ kicks around the idea that if you get Dolby it may not matter. Especially on a soundbar.