Here is a thread on that:
http://mytabletennis.net/forum/forum_posts.asp?TID=47138&PID=585528
And here is a quote from a review of that blade:
"AspitDemon said this on April 15, 2010:
Cons - Possibly splinters across the head of the blade. Recommend blade sealing.
Pros - By far the best blade I've use for the price. Not outrageously fast (I have added Tenergy 05 with it), and control was easier than expected. Stiffness wasn't hard, and exceptionally good for something like this."
That review comes from here:
http://www.tabletennisdb.com/blade/stiga-offensive-wood-nct.html
I think sealing is a personal choice. You only seal if you want to. Not everybody does. I like my blades sealed. With the Ebenholz where there is definitely a coating on the outside of the wood and the wood is hard, smooth and seems almost polished, I chose to seal anyway, and not for the reason's I usually seal a blade.