Based on selection of file type conditional validation is applied
{{userInfoFormGroup.controls.fileType.errors.extension.message}}
If you want to apply conditional validation on 'Image File' then you need to add 'File Type' input as 'Picture'.
{{userInfoFormGroup.controls.imageFile.errors.extension.message}}
If you want to apply conditional validation on 'Document File' then you need to add 'File Type' input as 'Document'.
It allow only doc or docx
{{userInfoFormGroup.controls.documentFile.errors.extension.message}}