Tora The Alter

Since the sign specifically shows an aerosol can, they might be banning not liquids, but pressurized canisters. Changes in atmospheric pressure can cause pressurized cans to leak or ignite during flight, so even if Dodo Airlines doesn’t fly high enough for that to happen, it’s safer to ban them as a safety precaution. 

That said, the reason your aerosol can doesn’t explode in your luggage is that all large passenger planes are pressurized. The Dodo Airlines plane however, is very very small. Even accounting for Animal Crossing’s ‘Tardis effect’ it uses for all vehicles and buildings it’s still clearly a small seaplane. Some small planes can be pressurized, while others are not. How do we know that the Dodo Airlines isn’t pressurized?