The TDMS file does preserve the timing information for a waveform, you can see it if you go to the 'Properties' tab. The attributes are there to calculate the waveform timestamp data, however, it does not look like the code behind the TDMS file viewer supports displaying the timestamp values in a column on the 'Values' tab. This seems like a good case for filing a product suggestion. As for a work-around, if you are set on using a TDMS file and viewing the timing information you would require a custom version of a TDMS file viewer.
-Bob