Right, I saw that was claimed. I didn't check timezones, etc but assume that is correct. Still, the interesting point remains that any tweet can be turned into a bitcoin-related topic.
As far as I understand it, the purpose of bitsig.io is to put any arbitrary text into the blockchain. This makes the statement trivially true, akin to saying that any tweet can be turned into an architecture-related topic by spray-painting it onto the side of a building.
Bitsig.io doesn't put arbitrary text into the blockchain. Given a string, if a Bitcoin address exists with sha256(string) as its private key, bitsig.io will publish the string, address, and first time the address was used. It also has tools for facilitating transactions to such addresses (which should never be used to store money). Hence stuff like this[0] from before bitsig.io existed.