The FAD assesses the relationship, if any, between a product or ingredient and the reported adverse event.

What does the word assesses mean I'm this context?

I would like to ask about the assessment of AE: causality. I have found that some sponsors provide to investigators only the option to select "Yes" or "Not" without providing the five options usually available: definitely, probably, possible yes, possible not, not related but having only "Yes or "Not" wont add "bias" for this assessment? it is not mandatory to have at least the definition of all the options?