Certain infectious bacteria have the ability to sit dormant for months, even years, add water and they come back.
It is true that many bacteria are ubiquitous and are useless to try and disinfect out, Aeromonas, and viruses like Lymph are always present, waiting for lowered resistance in fish.
Some phages however, are problematic and should be disinfected out.
How was the diagnosis of dropsy made?
Was a lab test done to certain it really was Aeromonas?
If it was something else (and I say this because many pathogenic fish bacteria show similar symptoms) I might not take the chance, of not disinfecting.
If it were say, columnaris, I would disinfect before using the tank, and substrate again, because columnaris can sit dormant in old dirt, and reinfect, wiping out a tank.
Since the substrate is dry, it will need to be cycled to get the good bacteria back anyway.
You have nothing to lose by disinfecting except time, and the cost of a dechlorinator after its done.
And the gain will be a pathogenic bacteria free tank.