When I search for "seamless texture" (specifically wood grain in this instance) a lot of images that do not make seamless textures show up in the search. So many in fact its almost imposible to quickly find the right wood grain.
Seamless should ONLY be attached to images that can be used for 3-D rendering materials programs, or illustrator to turn into actual repeatable patterns. Images that have gradation/shaddowing to them, or the grains don't match on all 4 edges should not qualify.
Very frustrating when you are working on a tight deadline.
I would like to suggest you to provide more keywords "seamless texture wood grain" etc. More keywords will refine your search results.
The problem is "seamless", not "wood". You will indeed find many textures that are not seamless by using the seamless keyword.
The only workaround that I have found is to download the preview and test in Photoshop if the texture is seamless, which is time-consuming.