I installed the Putco on my ‘19 Rebel, there is a delay. I used the Curt wire harness for my install. The regular tail lights and trailer lites, plugs, 4 pin/7 pin are on different circuits, hence the delay between brake and turn signals between light bar and regular lights. If you do not want any delay you have to wire the light bar directly to your tail lights and not the trailer plugs. It is in the directions for the Putco light bar. I am not keen on cutting into my factory wire harness so I live with the delay.
So you used the Curt Harness and the not the PUTCO harness... that may be why you have a delay.
The extra wires on the PUTCO harness may be going back into the 7 pin plug...