The definition of stablecoin is associated with fiat money as opposed to the volatility of Bitcoin.
L-BTC is an IOU, I agree, and I will never deny it, but if you understand how it works and its risks, it is another scaling solution, I will never say that L-BTC is Bitcoin, LN-BTC for example is Bitcoin.
But from there to say that L-BTC is fiat, I do not think it is fair beyond creating controversy in the same way that it is not a stablecoin.
When a better scaling solution comes out (as I think ARK is) do not doubt that I will use it and stop using worse solutions.