Mary will correct me if I'm wrong but the main reason low tow is taught
afaik is for cablerelease malfunctions.
If the gliderpilot is unable to release the tow cable he will signal this to the towplane and assume low tow position. This will enable the tow pilot to take the tow combination back to the airfield and land in the safest way possible.
This enables the glider to land first, at which point the tow pilot can cut or release the cable and land ahead or go around.