Saddle fore-aft position

First, welcome to BT!!

Now ........... there is no truth to the saddle position dictating the cadence.  Cadence is simply a matter of spinning your pedals, not the position you are in.  You will see various people do both high or low in either position.

There is also no way to "save muscles" for the run other than cutting back your effort on the bike and managing your speed.  There are some tri bike manufacturers that do not prescribe to the 76+ degree positioning and the people that ride those have just as much possibility to run well off the bike as everyone else.

If there was some magic saddle position that allowed the fastest run split afterward, every manufacturer would be using it.  There isn't.

Especially when you consider the way people will physically move fore and aft in the saddle depending on the course/wind/fatigue on their own!

The more critical thing to remeber in your set up is the overall aerodynamic position with regards to the amount of power you can generate in that position.

If you can give yourself a low overall cd and use the right equipment to get a low crr, then you can effectively generate less power to go a better time which will then allow you to conserve something for the run.