There is not as much difference in these two frames as the individual tube sizes would suggest. I see the Foil Stack height is 1 cm lower at the top of the head tube and the Reach is about 4 mm shorter than an old chart on the Six13. So it would appear to me at least, that a 56 cm Scott Foil has a slightly smaller frame than a 56 cm Six13. It is only millimeters here but it really shouldn't be an issue. I am wondering why you thought you would need a smaller stem with the Scott, was it based on the less than well informed opinion of some teen or twenty-something bike shop employee?

Instead of taking all these tube measurements individually, you should focus on Stack & Reach, which are nearly identical (within a few mm) between these two frames. Also note that the BB Drop of a Foil is less than a Six13 it's only 2 mm but that means 2 mm higher COG.