Changing Roku Audio HDMI value affects the CanDecodeAudio() function.

Hi All,

I have connected my Roku Stick to a normal LG Monitor with no inbulit or external speakers attached.
When i checked the Audio HDMI settings it shows Auto detect, Detected:Stereo . And when i run the code

CanDecodeAudio({"codec":"eac3"}).result

returns me false .
Now when i change the Audio HDMI settings to Dolby Digital Plus, and run the same code it returns me true . This is very confusing. Wasn't it that only some model of Roku Ultra and Roku TV support native decoding of DD+ ?. Why does my Roku Stick says it can decode DD+ ? Is it not a passthrough device?
Am i misunderstanding the api meaning CanDecodeAudio() . Please let me know

Thanks