TEXT vs. MTEXT DXF 50

[R.K. McSwain]

Why does DXF code 50 for MTEXT change depending on the UCS, but the same DXF code for TEXT does not?

Below represents results of querying a TEXT entity and an MTEXT entity created at the same rotation angle (45°).

* WCS
TEXT = (50 . 0.785398)
MTEXT = (50 . 0.785398)

* UCS (WCS rotated 45° about the Z axis)
TEXT = (50 . 0.785398)
MTEXT = (50 . 0.0)

Am I just overlooking the obvious here, or is this behavior documented somewhere?

Thanks.