Different results between true position and bilateral true position for an oblong

Different results between true position and bilateral true position for an oblong

Hello,
I noticed that I wasn't getting a consistent value for the bilateral true position of an oblong.
The 2 examples are made with the same reference frames.
We can see that the Z position is the same in the 2 methods (0.022) but the bilateral true position value doesn't seem to be consistent (0.141 instead of 0.046).

Are the oblongs calculated differently between the 2 methods?