This is completely correct. One of the first sentences in the 7110.65 (the FAA document governing ATC rules in the US, often referred to as "the book" by controllers) is "the primary purpose of the ATC system is to prevent a collision involving aircraft operating in the system." Loss of adequate separation between aircraft (called a "deal") is much worse for a controller's career than being inefficient.

In a world where airline regulators weren't captured by the industries they regulate, this would be iron-clad. In the real world, where humans live and make decisions, not so much.