My uncle, a Scrabble nut, proposed this exact derivative game to me well over a month ago, it's amazing to see ideas emerge in parallel. Feels like "if you've thought of it someone else has already" is more of a Law then a quip at this point.
I guess you could say the question isn't whether your idea is unique, but whether you've put in the time and effort to develop it, and whether your execution is good.
Hard agree. 15 minutes after my very first tweet about my variant, somebody else announced theirs with the exact same concept! I mean what are the odds?