Nate - thank you for your honest feedback. We read every review and try to act on any concerns that are raised. Because the product has so many applications and uses, it is also helpful for us to see how people are using it. The issue you are experiencing is a limitation because of the way the vehicle is designed. The OEM's (in this case, Ford) almost never output a turn signal for both left and right indicators directly to BOTH tail lights. Consequently if you need turn signal output for both Left & Right such as with the XK Glow 5th wheel light, you would need two adapters.
When designing the product, we explored the possibility of drawing from a source that had both turn signal outputs. The issue was that it would have required the customer to run wiring all the way up to behind the dash (this is the first place where both Left & Right turn signals are found in the same connector). This would have made the product significantly more difficult and expensive to install. Additionally, we get alot of customers that just need the parking or reverse circuit, so it would have over-complicated the product for many. All that said, we have made updates to our product description to better explain this concern. If there is anything we can do to make it right, please reach out to us at sales@starkey-products.com. Thanks again!