Not entirely. Having to use android drivers meant having to use android HWComposer, which meant ditching X for Wayland which can use custom file descriptors, and shifting to QT5 because it supports GLES2.0 scene graph, which meant Qt Quick 2.0 had to be used. No idea what the Sailfish UI was originally written in, but if it was Qt Widgets then very little can be reused, as its a completely different way of defining UIs. This is the specific situation that was being referred to, and it sounds like a bucket load of work to me. Switching major frameworks is not something you can handwave away.