Channel issues are like 90% of issues like this, but it's not always user error. Often a cheap production will just ship the front left + right channels as the stereo mix, instead of down mixing all the left + center channels into the stereo left etc. This is endemic in back catalogs on streaming providers where the catalog is a bulk assets that nobody reviews and is passed around between companies that don't care about the quality they deliver to each other.

That seems like a terrible default, aren't most people listening in stereo at best?

This is basically the issue.

User error but blaming the service to make an ideological point.

The dialog is just fine if you have a surround sound system or spend 5 seconds once to select stereo sound. Importantly, the dialog is still missing in the torrent versions taken from the surround sound stream because the same problem occurs. You only get the missing dialog in stereo if you download the stereo rip.