No requirements (coming from an FDA perspective). However, we utilize the approach quite frequently and it has been well received in FDA audits. It shows effort beyond mere requirements verification.
I’d say it’s more than what a developer do. Testers have (or should have) different critical thinking skills. They tend to ask “what would happen if…” That’s more along the lines of exploratory testing. If the system is designed to react after a certain button is hit, a developer will be sure that happens. An exploratory tester might hold one button down while pressing the specified button. It gives the tester some freedom to take alternate paths from scripted verification.