In this case, the following was true:

1.  There was a System Preference set that told TA to use the Break_Start_Date from the Source for the Gift Date, if it was available, instead of any uploaded value.  Here is the relevant text from the Help doc:
TA references the "Use Break Date as Gift Date for Pledge Uploads?" System Preference (under Background/Upload/Download) when the Pledge, Batch, and Account Data Upload procedures run. This system preference is specific to organizations that set up pledge break source codes (e.g., for television or radio pledge drives). If this system preference is set to "Y" for yes, TA sets the gift date for each pledge to the break date from the pledge break source code for the gift. If you enter "N" for no, TA uses the uploaded gift date.

2.  In this example, the Source for this Pledge had a Break_Start_Date of '1/2/2016', and therefore used that date instead of the date from the file.

To prevent this override, either use a Source without a Break_Start_Date, or remove the Break Start Date from the Source before uploading the file.

Here is the TA help article on the parameter:
Use Break Date as Gift Date for Pledge Uploads?