Unlike my previous player (Pioneer 578A) there is no manually selectable option for DVD-A vs DVD-V. It appears that it is up to the player to auto-detect. This is happening on all of my DVD-A discs, none of which are two sided. They mostly have two layers and playlists, one each for multi channel and 2 channel. Because the player is defaulting to DVD-V and the associated menu options for it, I can only access the 5.1 playlist. My interest is in the 2 channel layer and playlist.
I was able to reach Toshiba tech support and they knew less about my player and it's interaction with DVD-A than I did. They suggested returning it for a new one.