SONOS issues or other audio problems with channels and apps?

[stereohaven]

Just watching some of the horse racing on itv1 and I believe it should be in stereo but my SONOS (connected via HDMI ARC) is reporting Dolby Digital Surround 5.1.

General conversation and even adverts sound fine, but commentary in the last race was lost and muddy.

Is this an incorrect flag as reported previously on other channels (headend issue or something), or possibly a local issue my end?

[stereohaven]

Might just be me, the 3.35 race was fine, although still reporting 5.1 in the SONOS Beam 2.

Edited to add:

Now I am playing content on Netflix (I have Premium) and everything is presenting in Stereo that I select. This looks to be happening at a stream level because if I hit the i button to get the stream info, it is clearly stereo.

Obviously this is a minimum of 5.1 on any other device, why would that be?