the difference is that an machine analysis is necessarily limited and can't account for all the factors that make a text interesting. so it is possible that this analysis rejects texts that would not be rejected by a human.

it is objective but potentially biased. and it could even be discriminating if the input for this tool isn't diverse enough. but these are the issues that can go wrong with any use of technology, and we have seen many examples of that happening. however i don't think that is problematic if writers use it to analyse their own texts in comparison. it is however a serious issue if publishers use it to decide what to accept