Pretty hard to be thoughtful when there is literal walls between where the parent stood and where the kid expecting her to know he needed her help was.
His sense of entitlement and subsequent frustration and anger at her not coming to his aid had to be stopped before that little boy grew up into an entitled angry young man.
He knew better. I gave him a task to do one day and when he threw a temper tantrum at his sister for not jumping to his aid I let him burn out his tantrum and then commented to him that he must be awful tired after all that tantrum. He cautiously responded that he was. I commiserated with him and then informed him he still had the task to complete and oh, his sister was not his slave to be screamed at. I walked back to what I was doing and after a few minutes I heard a polite request to his sister for some help, which she did.
Teaching a child to ask for help also teaches them to later stand up for their needs in the adult world. Not to mention, learning to treat people with more respect.
Kudos. I learnt from your method.