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.