I wouldn't disagree that an initial big bang causes MAV. That's what happened to me.
However, VN and Labyrinthitis are old fashioned, wavy hand BS diagnoses to get you out the doctors office. There is no evidence that proves a virus causes the symptoms. The correct way to describe the initial big bang is 'acute peripheral vestibulopathy'. This does not assume an underlying root cause that is left to be determined.
I think an inner ear window injury due to barotrauma or hyperextension of the stapes apparatus is more likely the cause of these acute episodes.
I had such an episode after clear physical trauma. Mine lasted 5 weeks then apparently got better, only to return 5 months later as MAV/secondary hydrops.
It is the hydrops pressure that causes HF hearing loss and the tinnitus. This may be reversible if the hydrops imbalance is reversed.
Don't underestimate the physical fragility of the ear and the fine balance of its plumbing system. The inner ear window membranes are supposed to be some of the thinnest membranes in the body. It doesn't take much to damage them. Once you do its a complex recovery because leakage and competing pressure. This causes chronic fluctuating symptoms with multiple relapses.