Looking at the definition in the article, it definitely is a null result. However the example does illustrate that 'a null result' probably isn't a very interesting thing to talk about because it covers too many types of result. I think what people on HN actually want to track is something more like 'a boring null result'. The real question is whether there a process that is reliably being followed and leading to research that matches reality (where a statistically significant result suggests something is real) or is scientific publishing highly biased towards odd results (where studies that muck up or get lucky with statistical noise are over-represented).

In this case we would expect some studies of the minimum wage to show it increases employment regardless of what the effect of wage rises is in the general case - eg, some official raised the minimum wage while a sector went into a boom for unrelated and coincidental reasons.