Precision of specific values is problematic in many instances. Sometimes it accepts a nice 13 digit number... other times only 5... and then sometimes they truncate to whatever the decimal pace settings is... and then, some dialogs truncate to 3 digits. So the question really belongs to the operation you are expecting greater precision in.
I have asked customer support about internal precision of gear ratios at one time. I got a lot of different answers but in the end, even a simple ration of 1:3 truncates to 5 digits, including the 1 before the decimal. This is ridiculous for a mechanism analysis.
If you want to get to the bottom of this, I suggest you also file a support case to understand what you are really looking at.
I have also looked at equation curves with regard to precision. In working with an involute curve, I noticed that the starting end's tangency angle would vary significantly with the setting of my part accuracy. The default would yield a starting tangency angle at 3.x degrees! This should be nearly 0 in a perfect system, but even with extreme accuracy set, the best I could accomplish is somewhere around 1/2 degree.
I love using geometry to do, or provide the math behind it. However, I find myself questioning the results time and time again. So when something seems strange, I create a support case to better understand why I am seeing what I am seeing. Cumulative error in Creo is a huge issue.
