Focus Pages takes into account over 113 ranking factors when analyzing a page’s chances of ranking. It doesn’t just check to see if you have created Search Relevance (as in: optimized the text using the SEO Live Assistant or something similar that is offered by other SEO tools).
Focus Pages also looks at things like the keyword you optimized for, the snippet, how many shares you get for that page, Platform SEO, Platform Health, Social Signals, Inner Links, Backlinks, Page Authority, and much more.
The analysis is incredibly complex.
So, because it looks at so many different data points, the analysis will be different than the analysis run by other software.
Hence, the different optimization percentages/scores.