Is this actually true? Wasn't it fairly open to corporate abuse ; people getting paid by the state and working other jobs; and anecdotally, I know of companies who entered their staff on the scheme, but realised that their business wasn't as badly effected as anticipated after a week, but couldn't take their staff off of it for another two weeks causing loss of business and extra expense to the taxpayer.
There probably were cases of misuse, like all things in life. There was no real criteria for how badly a firm had to be effected to use the scheme. In fact that would have been very difficult to even judge at the beginning of April because no one could see into the future.
The more likely breach of the rules was that you couldn't furlough a worker and then make them do any work. If a business asked a furloughed employee to even do 5 mins work, that was against the rules.
3 weeks was the minimum period you could furlough a worker. It was designed that way to be flexible and not tie an employer into a decision for the long term. The claims were processed very efficiently in my experience, and I don't always like to give credit to the revenue!