The point is if they punish you (such as discontinue business relationship) because you send a request to obtain the source, and exercise the rights you've been

The point is if they punish you (such as discontinue business relationship) because you send a request to obtain the source, and exercise the rights you've been granted in the GPL, well, that's an additional restriction. I'm no lawyer, but the spirit of the law or a contract matters. You can't avoid a speeding ticket because the wheels of your car wasn't touching the road in the photo :)