Description is loosly defined it only specifies "Your function will take an input string that may contain any of the symbols "()" "{}" or "[]" to create groups.". Nowhere does it state that we should only test for grouping characters nor does it. If this is the purpose it should state it explicity otherwise should add other tests that include other characters.

Agreed, from problem description "Your function will take an input string that may contain any of the symbols "()" "{}" or "[]" to create groups.". Nowhere does it specify that it will only contain grouping symbols. This solution works because of either the problem is badly defined or it's missing test cases.