breaking the link btwn BTC the currency, from BTC the blockchain?
The "breaking the link" is pure marketing. You may be right that it is harmful marketing try to promote the idea of breaking that link. I consider it deceptive at best.
BTC-the-currency still has all 21 million on the main chain with or without sidechains. Some may be locked, some lost, some not yet mined, but they never go anywhere. They are on the main chain ever and always.
If you've read every post here Justice nailed it with this post.
https://bitcointalk.org/index.php?topic=68655.msg9448208#msg9448208I don't for a second believe Austin Hill thinks like you do.
Never has it been said anywhere that the link between the blockchain and BTC should be broken.
What Blockstream, and Adam Hill, are proposing is to allow the BTC to move between subchains and not be restricted to Bitcoin's blockchain features.
In the end, the BTC locked on a sidechain is still accounted for on the mainchain, as rocks has discussed.