I'm going to Media->Open Folder... and selecting the BDMV folder. Nothing happens, except the title bar flickers briefly. Checking the log, it has errors relating to VIDEO_TS or something similar, as though it's trying to treat it as a DVD.
No luck trying the folder containing the BDMV folder, either. Or with Media->Open Disc... and opening either of those folders while selecting the "Blu-ray" checkbox.