I would have a hard time being convinced that L-BTC is Bitcoin.
The fact that you can buy and sell Liquid with Bitcoin doesn't make it Bitcoin. By those standards, Ethereum is Bitcoin because you can easily peg in and out of it. Probably more easily than with Liquid.
By those standards, Ethereum is Bitcoin
No.
L-BTC only comes into existence when it is backed by BTC. There is no independent supply of L-BTC aside from that.
Its fundamentally no different than a fedimint from a practical perspective