I see no mention of STX, is there something I don't know or they won't allow smart contracts via the btc blockchain? Maybe I missread about them.
You can't allow any new smart contracts on bitcoin blockchain without changing the bitcoin protocol. What these projects do is that they usually create a completely separate blockchain and create a link between their network and bitcoin blockchain by creating some
bitcoin transactions that will remain in BTC blockchain. These are referred to as side-chains and STX seems to be in that category.
If you want my opinion, this is yet another vaporware.