Several years ago when I was on the B757, we pushed back (at LEPA) and got the wave off from the push-back crew with the pin being shown. As we started to taxi we quickly realised that something was wrong and the a/c was not responding to steering commands.
After a lot of head scratching and getting the ground crew back we had to shut down engines. We got some steps and had to wait for an engineer to show up. Eventually, the wise old engineer spotted the problem.
When inserting the steering bypass pin, a small lever has to be held back against a spring before the pin can be inserted. Normally, when the pin is removed the lever is spring loaded to latch back into place. However, on our aircraft, there was an accumulation of old grease and grime which had become tacky enough to override the spring on the lever.
When the pin had been removed, no one had checked to see if the steering bypass lever had clicked back into the normal position. The wise old engineer used the equivalent of some WD40 to clean the spring loaded steering bypass lever and 'hey presto', all was back to normal and we could get home.
So, when you see the steering bypass pin being waved at you, it does not guarantee that your steering will actually work. I always take it to mean that the last person hanging around the nose gear is clear of the aircraft and there is no ground equipment in the way.
Nowadays, when checking for the steering bypass pin from the lofty height of a B744 flight-deck, I would challenge even the youngest and sharpest person on the flight-deck to actually see the 'pin'. Maybe on a clear day with the sun behind you. As long as I see the black (with a few hints of red) flag being held aloft I will assume that the nose gear area is clear. As for the steering bypass being neutralised, I will look for some steering response before we have moved very far to confirm that all's well down below.