This seems to me to be based on an idea that you cannot pay costs for things if their effects will do nothing. This has been codified in Thrones and Star Wars (in Thrones it's known as 'the Janos Slynt ruling'). Essentially the idea is that it prevents you from trivially paying costs that may be beneficial to you.
In this case, the obvious example is vs Iain Stirling. Say Iain has 2 points and you have False Lead scored. On your turn you score a 2-pointer, but you don't want him to get his 2 creds at the start of his turn. Without this ruling you could just throw away False Lead at the end of your turn for no effect, but still gain a benefit for doing so.
Having this kind of ruling in place is good for FFG because a) it does seem strange that you should be able to 'pay' costs for no effect, and this kind of ruling keeps the focus on the effects of cards, which is good because b) it allows FFG to try more interesting things when designing effects with costs, without having to worry about those costs being abused.
I've not followed the history of Netrunner rulings closely enough to know if this is being consistently applied though. If not, we can legitimately complain here. I'd like to see a Janos Slynt-type ruling codified as in the other LCGs but it could be a while until that happens.