I disagree. A Rioter once said something to the effect that for skins they enjoy "skins that are an alternate interpretation of the champion. Skins that provide an alternative fantasy or explore a new or different aspect of the character". This skin idea does that wonderfully; it provides an alternative reality for Fiddlesticks, one were he appears to be a tranquil spirit of the forest.
It is far different from Elderwood Hecarim when we look at the details.
http://vignette4.wikia.nocookie.net/leagueoflegends/images/5/59/Hecarim_ElderwoodSkin.jpg/revision/latest?cb=20151119055536
Elderwood Hecarim is a gigantic Stag, taking form as a centaur-like spirit wearing stone ruins as barding, towering in presence, an ominous being great and terrible, threatening the power of nature.
Elderwood FIddlesticks looks entirely different. He looks organic, not looking constructed like Fiddlesticks normally does but appearing entirely as if he was grown, formed from wood that has spread and twisted together, that has grown over and collected what has surrounded it, like how plants actually do, reclaiming it for the forest. It looks like as if he has just developed from the growth of a flourishing tree, like a kind of Dryad of an Elderwood tree.
It's not just that this splash looks amazing but this is a wonderful idea for a departure from how Fiddlesticks is usually portrayed, providing an interesting "alternative fantasy" for the champion. It would be a shame to scrap this idea for only a one-note "creepy" interpretation of Elderwood, a niche that he already has good representation, just because it shares the palette of Elderwood Hecarim while Elderwood Bard doesn't.