I would use BTEQ (RECORDMODE, DATA options as in your example) because the table should be small. But FastExport (FORMAT UNFORMAT, MODE RECORD) would work too. Either way, since DataParcel is VARBYTE, the exported file will have a two-byte unsigned binary length field added to the beginning of each record.
Oh, I didn't pick up on the fact that your input was FORMAT VARTEXT with TAB delimiters.
The DataParcel field is the record sent to Teradata, but that is after FastLoad client converted the original text to VARCHAR fields, more or less in "FastLoad format" as you guessed: two-byte length for the record, two-byte length of the first text value, first text field, two-byte length of the second text value, second text field, etc.
I suppose you could EXPORT the DataParcel field to a file using BTEQ Or FastExport, then FastLoad it back to a table with all fields defined as VARCHAR, then EXPORT from that table as tab-delimited using SQL Assistant.