snapshotAsMesh gives wrong face area

I am running into a strange problem and wondering if anyone can duplicate it so I know I am not crazy. I have a spline in the shape of a rectangle with a square hole in it. They are both part of one spline shape. The large/exterior rectangle measures 20mx30m and the hole/interior square measures 10mx10m. If I convert the spline to a mesh manually and then send that to the code below, I get back the correct result (600 - 100 = 500). But if I do not convert it to mesh and simple allow the code to use snapshotAsMesh, I get 434.816 instead of 500!! Please see attached screen shot for evidence of what I am getting back. Any reason for this error? Is there something wrong I am doing or is this a bug in snapshotAsMesh? Thanks for your help.

fn getSurfaceArea obj =
(
local surfaceArea = 0.0
local objMesh
if (obj != undefined) then
(
if (classof obj == editable_mesh) then objMesh = obj
else objMesh = snapshotAsMesh obj
local objFaces = meshop.getNumFaces objMesh
for f = 1 to objFaces do
(
surfaceArea += meshop.getFaceArea objMesh f
)
return surfaceArea
)
return 0
)
myObject = selection[1]
surfaceArea = getSurfaceArea myObject
format "Surface Area = %\n" surfaceArea