Both Jam Jar & Club395 are mapped as separate nodes, along with all the other businesses which occupy the Old Malt House. I've double-checked businesses today in person with one of the Club395 managers. 
Seems like the default OSM Carto 'map' doesn't render amenity=events_venue, but they are all there, searchable and visible on apps which do show events venues, so you'll find them there on whichever OSM editor you prefer