All of these tools, including Moz - are meant to be taken directionally, not as scientific fact.
The popularity of these tools came about after Google killed pagerank and SEOers needed some sort of metric to obsess over and to prove to clients that they were moving the dial - even if the traffic or results weren't showing it.
So now we have DA and backlink #s which are all gimmicks popularized by the companies that created them to push their own products, when in reality these are more vanity metrics. The only thing that matters is how much traffic is it generating and how well is it converting.