Don't quote me on this cuz I'm not totally 100% sure, but I swear I read something about him not having the stupid 3rd one under the wrist anymore. I wanna say I think he had them coated in the red metal from that crazy red bladed ninja sword and he tried to kill Wolverine and failed, then Wolverine like ripped them out/removed them somehow. Either way, I think it's a stupid design. I'm ok with just 2 but the 3rd coming out under the wrists is stu-pid.
You are right: Recently, the claws which extended from the underside of each wrist had been bonded with a piece of the metal taken from the Muramasa Blade. The mystic properties of the blade enables it to inflict wounds greatly nullifying superhuman healing factors. Wolverine cut both of Daken's Muramasa steel coated claws out of his arms with the Muramasa Blade[31] and due to the properties of the Muramasa Blade, the removed claws have not grown back as quickly as they normally would.