Incorrect. It is possible to make 0 XRB transactions. I made a couple of them and they do appear in the block chain, so they have been validated.
An easy way to make a 0 XRB transaction is to use the full client (version 8 or 9) and to send 0.1 XRB. The client silently ignores the decimal part (looks like a bug to me) and creates a 0 XRB transaction that appears in the blockchain. you can see it with the RaiBlocks / nano explorer.