Some examples of threads that I felt were representative.
https://twitter.com/molly0xFFF/status/1513184187498569729
https://twitter.com/molly0xFFF/status/1516610542588284931
I think the most generous summary of these interactions would be that leashless is solidly convinced of two things: blockchains are the answer to pressing world problems, and skeptics are simply not on his intellectual and moral level.
The home page of Mattereum appears to be a pitch to create one NFT per physical item and then make transactions about it on the blockchain. I confess I am also unsure of how this technology adds value to e-commerce. Nor does this scheme seem to be sufficient to bring about such levels of transparency that it could meaningfully combat slavery, or address issues of climate justice. I hope that leashless is correct about all of that.