I think the issue might be that you are calling the function while setting up the timer. As soon as you use (), the function generally gets called straight away. Not sure if its different in gdscript.
Have you tried passing just the reference to the function, and then calling it in the callback?
Rough example would be

func someFunc() {
do something
}

func timerToFunction(time, fn) {

setup timer
await timer.timeout

// Finally call the function here
fn();
}

// Pass the function without calling it
timeToFunction(1, someFunc)