I always figured the radiant heat from the stone/tile roof of one of those brick ovens was what sort of stabilized the baking conditions in one of these. I think that with skill and experience the person tending the oven could get similar temperatures day in and day out... in part they can do that because the oven has so much heat mass, that minor or even relatively large fluctuations in ambient conditions will be dampened by the heat mass... Not only would the heat mass dampen variations in ambient conditions, I assume that the heat mass also tends to be one of the main heating forces at work, where the flames themselves would tend to blend in with the heat radiating from the stone/brick.
So... with a thin piece of stainless steel as the roof, I don't think you have that mass, and probably don't have nearly as much radiant heat either, so the flames themselves become the dominant heat source on the top side of the oven. When a cold wind blows and/or the oxygen to the pellets is reduced do to various atmospheric conditions, that flame source would very likely fluctuate in temperature, etc... So, without the thermal mass, my concern is that heating driven almost solely by the flame itself becomes less predicable. Especially since the amount of oxygen is governed by many external but mostly passive forces.. ( no fan ).
So, I see a real brick oven , being the stabilizer, and the thin sheet materials of a Uni as having little to stabilize the temperatures...