Every company has their pet schools. For the most part though, it’s confirmation bias. Your son is where he’s at because he’s sharp and has demonstrated that he works well with others. He may not have been at THAT group, but he would have had great opportunities no matter where he went.
My son works for a startup that has been heavily hyped in the tech and financial media. One of the cofounders has degrees from Cal and Stanford. One of the Chief engineers has a PhD from Caltech. They don’t have any other engineers from those schools, because they don’t recruit at any of them. They have more Cal Poly grads than any other institution (my son was the first and the first new grad they hired), but roughly half their employees were educated in Europe.
When he was contemplating switching to Stanford for his MS, multiple engineers on this forum said that they’d worked at companies that preferred Stanford grads, but had worked at just as many that favored Cal Poly grads. He stayed at Cal Poly for a funded, thesis based MS, which wasn’t an option for MEs at Stanford and got out a year earlier.
At the end of the day, most of a person’s potential success, especially for engineering, is baked in when they graduate from high school.