Yeah. It is an amazing bridge that took a few visits to realize all of its secrets. Thought it was a dark and huge bridge on my first visit and someone showed it to me. Took quite a few visits before I realized that those were consoles on the walls and the whole concept of up and ceilings doesn't apply to this bridge.
Tholian physiology enables them to walk on the walls and ceilings of their environment, for them artificial gravity might be a hindrance, they might neither require it nor want it on the bridge, their crystalline exoskeletal nature might negate the problems of muscle atrophy and bone density loss that afflicts humanoids in zero gravity. In any case no creature lives on the bridge and the effects of a duty period working in zero gravity would be negated when returning to a gravity environment when off duty. There is the possibility that the Tholians arachnoid nature resulted in a different design philosophy with their ships, with humanoids the highest level of their ships is at the top dorsal area with every deck below considered down, with Tholians the ships may have a central zero gravity hub with all lower decks that have gravity radiating outwards in all directs from this central location in a web like configuration.
This is all in game pseudoscience but could be used to explain the peculiarities of the Tholian designs.