The kinematic equation (d = v * t + 1/2 * a * t^2) assumes the acceleration keeps increasing throughout the given time t. So for example if you have a car that starts at a given speed and keeps a steady acceleration, this will tell you how far it will travel in say 30 seconds.
Using this analogy I some quick maths (using Excel) to see which equation would be most reliable. For a car accelerating at 2 m/s^2 from an initial speed of zero for 30 secs, with a 1.0 sec sample (dt) period, the final displacements are:
Using Platform Equation: 930m
Using Incremental Newtonian Equation: 900m
If the sample period is changed to 0.5 sec (ie analogous to using a 120 Hz monitor instead of a 60 Hz monitor) then we get the following answers:
Using Platform Equation: 915m
Using Incremental Newtonian Equation: 900m
If the dt is changed to 2 sec (ie analogous to using a 30 Hz refresh rate) then we get the following answers:
Using Platform Equation: 960m
Using Incremental Newtonian Equation: 900m
Conclusion (Revised) -
The Newtonian equations work, whereas the equation used in the Platform Behaviour produces inconsistent results.
Edited to correct some poor public maths...