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.
Still the level of investment and interest given it's quite high. Obviously you can not add yet if no future fork might happen to bitcoin smart contracts, but following the current chain and somehow cross-chain them would be cool.