From slack conversation:
"When exporting to CSV a field with “1” string type, CSV is being taken as boolean and shows TRUE in the table as you can see in thread.This doesn’t happens when you export data via the Shell with mongoexport command."

Data set has documents with a field with a string value: "1", "2", "3", or it's empty
Cases where the documents have "1" as the string value have their values as TRUE in the exported csv.