Your fire hazard concern is legitimate, and I would not leave it charging for that length of time either. The Battery loss of charge is going to happen, that is the nature of batteries.
That being said, this forum concern for "phantom" lost charge is unfounded. The way the Lucid battery setup is structured, the HV battery charges up the 12V batteries via the Wonderbox. When the car is not being used, the HV battery trickle charges the 12V batteries to maintain a constant 12.5 to 12.7 volts, so the 12V, AGM lead acid battery does not degrade and start sulfation on the lead plates. All lead acid batteries do this and have so since they were invented. In actuality this car, as all EVs, have a built-in trickle charger for the 12V batteries. On my ICE cars, there is no trickle charging as the battery is charged by the alternator. When an ICE car is idle or in storage, the battery loses charge unless a trickle charger is plugged in the battery, which I do, and unfortunately it is the only way to avoid discharging the battery, even if you take the battery out of the car. The only concern you should have is if there is a huge loss of charge, which may indicate a loss of charging capacity of the 12V battery or a problem with the 12V charging circuit from the Wonderbox. You just have to accept some loss of charge when the car is idle, knowing that the HV battery and Wonderbox are keeping the 12V batteries from permanently losing charge capacity.