Why do the UAS (LATCH) installation instructions state to connect one of the connectors before routing the UAS belt? 

The UAS (LATCH) connectors are “handed” – meaning that there is only one correct orientation for the UAS connectors and the adjuster side will always end up on the side of the seat closest to the passenger side of the vehicle. 

The UAS belt will need to be removed from storage and routed every time the Liingo is installed, so the instructions were written in a manner designed to create a systematic way to end up with the correct routing each time.