So just let it sit inside a pressurized tank where it will cause enormous pressure and blow up? Actually... If the tank is almost full then you might be good but if it's almost empty then you better take it out.
The tank is not pressurized. Not only is it vented, the cap is open. What you are talking about is called a "BLEVE". Boiling Liquid Expanding Vapor Explosion. This can happen with propane tanks and the like. That's when the pressurized tank is heated to bursting pressure.
Fire needs 3 things to burn. Fuel, a source of ignition, and oxygen. The last thing you want to do is expose as much fuel as possible to oxygen which is what happens when you take the nozzle out. The fire will probably be contained to the fill tube as the vapors come out but being as there is not enough oxygen in the tank to sustain combustion the fire won't travel down the fill into the tank.
The fire will cause the gas and air to expand faster than anything can leave causing it to become pressurized. The air isn't pressurized around a grenade but when it goes off...
The gas tank is not a sealed vessel. It will not become pressurized to the point of rupture. But if, god forbid, you find yourself in that situation you go right ahead and pull the nozzle and spread the fire as much as possible. What do I know, I'm just a firefighter trained in such things.
Guess who else is gonna never see me again
Fire needs 3 things to burn. Fuel, a source of ignition, and oxygen. The last thing you want to do is expose as much fuel as possible to oxygen which is what happens when you take the nozzle out. The fire will probably be contained to the fill tube as the vapors come out but being as there is not enough oxygen in the tank to sustain combustion the fire won't travel down the fill into the tank.
Fast forward to 3:47 to see what happens when you remove the nozzle.
A better example.
You do you bud.