Any reference to constraints that limit creativity is just another way of equating creativity with self-expression, an erroneous and irresponsible idea. Except for personal projects, self-expression has no place in design, but constraint is vital to design. No component fuels creativity more than constraint. Indeed, without constraint, creativity (and design) is irrelevant. The discovery process is mostly about finding constraints, which is why we must do such a thorough job of it.
Constraints are a designer’s best friend. They’re signposts, not shackles.
The article as a whole reduces the magic of art a bit too far for my taste. Not all creativity is in service to a client. But even so, I think the importance of knowing the constraints of your medium is critical.