You're English is great. I think that the FAQ breaks it down to mean only the Impaler or a siege weapon missile will harm undead. The "arrows, crossbow bolts, slings, darts, etc." covers just about everything else, including thrown weapons. A thrown weapon does not deliver anything close to the damage of the Impaler. The Viridian axe might come close however. Technically you're right, there should be perhaps an even more detailed description for all of us, native and non native speakers alike.
I'm hoping some of the more experienced people on the forum chime in, but I'm pretty sure that's how the rule works. Undead are supposed to be scary, and watching missiles bounce off of them balances out with the fact that they are typically slow movers. I hope this helps. Cheers.