Do you know or are you just saying? The car would start, just not easily. I would thnk if the ignition switch was unplugged, it wouldn't start at all.
Me, me, me..I know this..
The harness where you found this connector is part of the starter harness. It runs under the motor to the starter, it also grounds to the frame and provides the battery wire and also connects to the alternator.
The connector you mention, runs all the way down to the starter.