If the fan is always running, very slow to maintain the temperature, the risk of flashback or backdraft should be reduced, but I'm not a pyro expert. Even pyro experts make mistakes (e.g., prior US requirement for fan on flour silo to reduce explosions). It seem like the main risk is when a sealed container is opened and introduces air to super heated fuel (like on a Kamado). Possible turning on the fan to have a controlled burn of the gases for a few minutes, turn off the fan and open the door. I think only time and experience will tell. The kamado is thousands of years old and we still finding things out today.
I think Pellet's fan is a brushless DC computer blower. So sparks from the fan should be minimal from static or friction. A fixed steel screens can be added to less the chances of a spark from the fan to ignite the gases in the firepot.
Is the reverse flow for Pellet's firepot is the air flow goes down instead of up?