Answer
IFS isn't adding anything incorrect — this is standard CSV escaping: a field containing a literal double-quote character has to have that character doubled and the whole field wrapped in quotes per the CSV format, which is exactly what you're seeing when viewing the raw file in a text editor (Excel just hides this and shows you the clean original value). The migration import itself correctly interprets this standard CSV escaping and stores the true original value. If you'd rather sidestep CSV escaping entirely for data containing quote characters, saving the source as a plain tab-delimited file and setting the migration job's column separator to tab avoids the need for quote-escaping altogether.