W.O.T in neutral

[Loren]

It would bang the rev limiter at about 6200 rpm.

Some cars have a secondary rev limit that kicks in at a lower rpm in some conditions. (like my old Saturn limited to 4k if the car wasn't moving) Not sure about the Yaris.

Modern engines are designed to basically not harm themselves. You can bang the rev limit for quite some time without hurting anything. Now, if you botch a shift and do something like grab 2nd gear when you were reaching for 4th after revving out 3rd... that can over-rev and do some damage. (if you have an automatic, the ECU won't allow such a downshift, it will delay the downshift it until it is safe)

Wanna see what your Yaris will do if you drop it into neutral at speed and keep the hammer down? Try it! Seriously, you're not going to hurt a thing, just make a lot of noise and scare pedestrians.

If you actually HAD a stuck throttle, you'd probably want to kill the ignition when you went to neutral and just be aware that your power brakes are going to go away very quickly due to no vacuum. (you can still stop, it will just take more pedal effort)