Lineage OS for Sony devices is based on proprietary Android blobs. This means that the blobs are extracted directly from device and, if needed, patched or replaced with some similar blob.
Jolla has based its ports on AOSP version of Sony Android (SODP). This one has a different set of blobs and a different team working on it. What makes this version extremely attractive for Jolla is a clear licensing policy by SODP and that allows you to legally build on top of it what you want. For example SFOS. Unfortunately, requirement of having blobs and basing all SFOS on this Android has become rather problematic. It has lots of bugs, small team that works on it when they can. As a result, SODP based Android is rather unstable, lacking features, and driver support. For that reason, already a while ago, Lineage devs switched to stock-Android based approach. That maybe not possible for Jolla due to legal aspects.