I busted this myth some time ago, but here's some figures to prove it's hysteria.
When looking at these type of myths or proving anything racing related, I like to look at favourites, as patterns can easily be seen without form factors creeping in.

All Favourites: 31.52% S/R

First Starters: 35.97% S/R

First Uppers: 32.75% S/R

Second Run: 32.62% S/R

Third Run: 32.12% S/R

Fourth Run: 31.26% S/R

Fifth Run: 31.31% S/R

Greater than five runs: 29.42% S/R

Basically second up, the strike rate is better than all favourites.
The difference between first, second and third up is less than 1% using a sample size of over 150,000 favourites.

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