This is working as designed. As per the Survey Publishing feature, Survey_Target_vod fields are updated with the values from Survey_vod for

• Territory_vod
• Start_Date_vod
• End_Date_vod
• Frequency_vod
• Region_vod
• Language_vod
• Any custom fields

that are added to both Survey_vod and Survey_Target_vod that use the same API name.

Related Documentation:

CRM Help Documentations:

• Adding Survey Target
• Publishing a Survey