Learn English – A more formal alternative for “go with” in the context of food or literature

I think that the phrase make more concrete is perfectly acceptable. You shouldn't worry too much about repetition if the word or phrase is correct in the context.

But since you're looking for more options:

• Crystallise - make free from confusion or ambiguity; make clear; — The Free Dictionary

• Make (more) tangible where tangible means able to be touched.

• Elucidate - to make clear or plain, especially by explanation; clarify. — The Free Dictionary

• Materialise - come into being; become reality. — The Free Dictionary

I think you are dealing with a real bad case of confirmation bias.

Confirmation bias, also called confirmatory bias or myside bias, is the tendency to search for, interpret, favor, and recall information in a way that confirms one's preexisting beliefs or hypotheses, while giving disproportionately less consideration to alternative possibilities.

That being said this person is clearly unqualified to make OR deny a diagnosis.

References:
https://en.wikipedia.org/wiki/Confirmation_bias
https://en.wikipedia.org/wiki/List_of_cognitive_biases