Figured it out. Apparently, you need to Series.Points.AddXY(xValue, CenterMarkerInErrorBar, LowerBoundsInErrorBar, UpperBoundsInErrorBar)
.. But that wasn't documented anywhere that I could find from Microsoft.
Also, if you see the above information, you can't use the first two lines, as they'll break the error bars .. somehow. The last two lines and the code in this post will work fine, though.
Special thanks to MSChart C# Error Bar Graph With Dynamic Upper and Lower Bounds for the answer!