Many of the Bitcoin sidechain projects seem to come either from the Ethereum world or from the Ordinals/Runes "scene", where premines are seen as completely normal.
There you go, you nailed it. The entire Ethereum project is built pre-mined. Pre-mining in second layer is seen as completely normal, because the main layer is pre-mined itself.
And just to be even more clear: It doesn't make sense to name it "layer 2", if it isn't reusing the token of layer 1. You either reuse the currency, or you're creating a brand new. In the latter case, there's very little reason to build it on top of another layer, and not recreate another layer 1.