When creating a Rule with a Query condition, you must check the "Apply to plurals, synonyms, and typos" checkbox in order for your Rule condition to consider synonyms for that query.
If you've checked this box and notice that the Rule is not always triggered for all synonyms, this may be due to a high volume of synonyms in your index for the query term.
The Algolia engine explores all of the alternatives and exact matches of the query under a timeout to find the Rules that match the query. For a term with many synonyms, the timeout may occur before the rule is triggered.
If you observe this behavior, you might consider reducing the number of synonyms for the problematic term until the timeout is no longer reached.