Hey whl6868,
According to page 157 (or 3-135) of the manual (http://www.ni.com/pdf/manuals/370132c.pdf), there is no default value for VI_ATTR_VXI_TRIG_STATUS. If Resman is returning valid values for it, then it must be actually reading the lines. Else, I would only expect it to return valid values when you actually call the function yourself.
Regards,
David R
Systems Engineer
National Instruments