The danger is similar to any backtested algorithm. You can always go back and find theories to fit your data. That doesn't mean they will be predictive going forward. It also doesn't mean they _won't_ be predictive, and I would say they can form a good hypothesis for a new experiment. It's not that it's meaningless, it just lacks the power of scientific evidence. It's comparable to a non repeatable experiment, where the hypothesis counts as a first "repetition".

At least that's my interpretation as a non statistician, but I think there's a difference between statistical significance and scientific proof. The findings may be statistically significant without actually proving anything.