You didn't say that you actually tried running a hose into the tank. Try it. I'm not so sure there is such a thing as an anti-siphon lock. If you can run the hose into the tank - you win.

There are some things that help control fumes kicking back which might interfere with running the hose down the fill pipe. There also can be some interesting piping configs for the fill pipe that make a hose tricky to push to where it should go (my car).

Don't assume something won't work unless you've tried it or you have vehicle-specific info from someone you trust.

If you're not a mechanic and able to avoid setting your car and house on fire as you try things- then stop reading here.

Think about it- how can the mechanic remove the fuel from the tank when the vehicle's fuel pump has failed? They have ways which might involve a hand pump or a siphon. (that's the case for my car which had a pump seizure)

A way for the modern car (with electric pump located in the fuel tank) to dump fuel (which is what mechanics use when the car's pump DOES work ) is to open one of the quick-connect fittings under the hood, connect up a hose with matching fitting and route that hose to a gas can. Then find a way to make the fuel pump run continuously. (service manual should explain using either a general purpose diagnostic computer to command it to ON or find a way to supply power to it separately from the usual switched power supply)

I've pumped out an '85 Chevy prior to dropping the fuel tank for a pump change in this way.

My dad has an '85 Suburban (old style fuel pump external to tank). He's added an external electric pump for vapor-lock prevention. It also means he can pump fuel to a gas can as needed by disconnecting one fuel line. Has proven handy for generator fuel supply.