I'm with Ben, and I think that either the description you received is wrong, or your understanding of it.*
There is to my knowledge No Mechanical Connection between starter motor and steering lock.
What you actually have is 'shift lock' which is pictured above.
You can should only be able to start an automatic with it in Park or Neutral. (Certainly in 2 of my V8s, the Park position doesn't always go into Park if the gear selector was pushed to gently). This is all because of starter solenoid lockouts.
With shift lock, you cannot remove the ignition key if the gear selector is not in park. You will see that when you turn the key anti clockwise to off, it doesn't quite move far enough until you place the gear selector in park. Now you can remove the key.
If you turn the ignition off with the gear selector in neutral, you cannot remove the key.
It's a security function of sorts. With the key removed, it takes a lot of work to move the car as the transmission is locked.
Once the gear selector is in park, you cannot move the selector out of park unless you press the brake pedal. It's a safety measure of sorts- most folks with automatics park the car with the gear selector, and the handbrake is never set. If you could go straight from park to drive without a brake set, the car could move unintentionally.
Here is the ignition lock/steering lock
And in Ben's diagram above, item 42 is a cable that links the gear selector to the ignition lock. That cable moves a lever on the top of the steering lock, which stops the key from being removed if the gear selector is not mechanically in the right position- Park.
Electrically, there are a few issues, as my V8 project keeps giving me.
The car must also detect that the gear selector is in either Park or Neutral to start. Otherwise, the starter won't work. As I mentioned, if the gear selector is not pushed positively into park, the indication on the instruments is that the gear lever is still in another gear. Reverse.
Another mechanical problem, which is where you might be having a problem, is that after starting the engine, the key doesn't always return to the run position properly. This has left me with the starter still engaged with the engine running. After a little investigation, I believe this is related to the ignition lock barrel, rather than the 'shiftlock'. However, I've not had time to look into this any further.
*of course- my understanding of all this might be flawed, too!