You are on the right track. The author could have simply said "reactive" – perhaps they avoided it because “reactive” has other connotations (chemistry).
In this case the quote marks are used to show that the author is using his or her own definition of “reactionary”, not the dictionary definition you referred to. Some advice about using quotation marks - it is a matter of style, so be careful.
To use “reactionary” to mean “created in response to something, a reaction to something” is a natural step, based on the meaning of “react” and “reaction”, so I think most native speakers would understand the author.
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