For example it looks to me like it thinks fhtagnblue which has the words tag and blue in it should return true? Maybe I'm reading things wrong - but if it should return true, thus allowing fragments, then every word with two letters or more would return true because every letter is a noun.

If it is as you said, which might be actually interesting thing to do and potentially even useful, I might not want to do it with a query this dictionary for a string and instead have actual access to the dictionary to work with since I figure an optimized solution can be made with binary search.

on edit: I mean considering Google's reputation for trick questions and logic gotchas I would probably just say "wow you guys really are like that" and write something like

if(!s) {return false;} s_array = s.split(""); return s_array.length > 1;