Consider it this way;
Elves are dedicated to the preservation of nature. Although their goods are mostly wooden, they are constructed only from naturally-fallen wood, as evidenced by their attitude towards tree-felling as practiced by humans, dwarves, etc.
Dwarves are masters of crafting, and will dedicate themselves to the shaping and crafting of high-quality items using intricate toolwork, cutting, carving, etc. They all have a preference for metal, but many can and will turn their attention to other materials.
So it's perfectly normal for dwarves to create some items from wood - indeed some constructions can only be built from roughly-hewn logs (windmills, waterwheels, axles - all staples of good solid Dwarven engineering, but I don't hear anyone calling these elven!)
Personally I prefer to view it as when the elven traders come to my fort, passing the stumps of fallen trees, along the rough log palisade wall around the fortress, past the creaking and groaning windmills and waterwheels straining their axles to power dwarven heavy industry, around the path beside the smoke-belching wood furnaces and sawdust-covered carpentry workshops, finally reaching the masterfully built rough log trade depot to unload their goods - to be greeted by my broker, a Legendary Woodcrafter, who warmly welcomes them to the fort and tells them all about his profession to pass the time whilst my haulers bring crudely cut wooden bins full of xClothesx to the depot for the elves to take with them as a memento of their visit.