It’s a serious accusation which logically has a high standard of evidence that is hard to meet, requiring some knowledge of intent. A publication like the Economist cherishes its reputation, making it more risk-averse about making accusations it can’t back up. Until these people provide circumstantial information like doing something illegal and fleeing to Russia, it will be hard to make it stick.

Anyway, Russia doesn’t need to put most of these people on the payroll to make good use of them.