Original User: Jian
For coordinate systems other than Web Mercator or geographic CS, this is by design, since there is no better way to do so.
Computing geodesic area/length is only possible with Web Mercator or GCS. Under other CSs, it reprojects the corners (xmin, ymin, xmax, ymax) to GCS, and interpolate the mouse position to find the approximate location under GCS in order to make it possible to calculate geodesic area/length. It is simply not possible to reproject the mouse position point while it's moving. After the drawing ends, as you observed, it shows the accurate result.
The better way is to write a projection conversion for this specific needs.
BTW, your attached image shows 1018feet, instead of 1108.