I'd love to have someone with firsthand knowledge fill me in here, but: I've seen Flash-based feature phones do all kinds of things that desktop Flash struggle

I'd love to have someone with firsthand knowledge fill me in here, but: I've seen Flash-based feature phones do all kinds of things that desktop Flash struggled to do on (then-contemporary) desktop PCs. I can only conclude that Flash Lite had a significantly different codebase than desktop Flash, with very different performance characteristics. Just because "Flash could do it on a feature phone" doesn't mean that a smartphone could keep up with the full Flash plugin. Look at the performance disaster that Flash on Android was.