This is basically a bespoke blockchain that uses BTC as oracle. It's not a smart contracts "on Bitcoin". By this logic, I could write an ERC20 token on ETH and use some BTC state, and call it "smart contracts on Bitcoin".
For using Bitcoin state on Ethereum, you'll need to implement Bitcoin SPV proofs. It's entirely possible but fairly complicated to do that given (a) Ethereum is a separate network that can fork independently from Bitcoin (Clarity contracts on Stacks fork with Bitcoin), and (b) Eth miners have no native visibility into Bitcoin state (Stacks miners have full visibility into Bitcoin state). Possible but more complicated. Further, any asset generation and transfers etc on such ERC20 asset would have nothing to with Bitcoin vs on Stacks all asset generation and transfers etc settle on Bitcoin and are secured by the Bitcoin main blockchain.
The lessons we learned from that deployment for 2+ years is that (a) it doesn't scale that well and (b) it's very hard to modify Bitcoin and get new changes accepted (for good reason), so you end up with very limited scripting.
To fix the two limitations of Stacks 1.0, we worked on Stacks 2.0 which has a separate blockchain (so scalability independent of Bitcoin) where settlements still happen on Bitcoin and, more importantly, a full smart contract language without modifying Bitcoin itself: https://clarity-lang.org
Definitely not a fan how you're trying to bend reality for marketing benefits.
Everything in cryptocurrency is so obtuse and unapproachable for even otherwise-technical people, it’s pretty incredible given it’s been around over a decade now.
And isn't it a two-way pegged sidechain?
If you spent decades working on video game graphics, would it surprise you that someone describing algorithms for sophisticated quantitative finance or high frequency trading use terminology you're not familiar with, including an abundance of words literally borrowed from the Greek language?
Information technology is an absolutely massive field that is finding more and more use cases every year, it shouldn't be a surprise that there are areas of it that you're not familiar with and would need to devote a substantial amount of time to become well versed.
As someone who has spent a decent amount of time understanding cryptocurrencies, it's not really all that much different from learning any other field. You can start with some Youtube videos, read a few blog posts, heck you can even spend a couple of weekends writing your first smart contract and deploy it to Ethereum to see how it works. My first side project on Ethereum was writing a decentralized poker game, I wrote a series of smart contracts based on the theory of Mental Poker [1] and deployed it to the test net, and then wrote a web front end for it that waited for a new block to get published, parsed it and displayed it. It was pretty cool, once you deploy your smart contract to the blockchain, it's kind of magical seeing a completely decentralized system of computers bring that code to life. Like once you deploy your code, that's it, it's entirely out of your hands from that point forward and there's this engine that takes it and keeps it chugging literally for as long as there are miners willing to operate the Ethereum network.
Everything is a mystery until you take the time to learn it.