Fields such as Gender still show in the Import process, even if they are removed from the batch template that the import was created from. Therefore there are more fields in the Import map fields screen than in the Batch select fields and defaults.
The Gender field is showing up in import because it is specified as a FieldToInclude on the Constituent Update Batch default. These types of fields are required to be in the batch template. If the field is not selected by the user in the template and the field is specified as "CanBeHidden" on the batch specifications (which the Gender field is), then the field will be included as a hidden field in the template. Thus, in this case, even though the Gender field is not selected in this template, it is included as a hidden field in the template. All fields, hidden or not, appear in the list of mapped fields when setting up an import.
Steps to Duplicate
Go to the Revenue section, and select Batch entry
Select Batch templates, highlight the Constituent update batch, and select Edit
Go to the Select fields and defaults tab and either remove the Gender field from the template or confirm it is already removed
Save this change, highlight the Batch template, and select Create import
Select the Map fields tab and note that the Gender field still displays as an option