His point was that you can be more open and easy going with junior employees. Letting an ambitious programmer lead a project of his own is pretty low risk.
There's also much more room for creating opportunity for one person without removing it for someone else.
In a business there's usually only one spot for a COO, but you can have many senior developers. Therefore the stakes are lower, because other members of staff don't see an opportunity vanishing when a promotion to senior dev is announced.
