The JIT is mature enough that this setting can be removed, falling back
to Unicorn only on unsupported architectures. Any missing features from
Unicorn (of which there are extremely few), are mostly
developer-oriented, which most users don't care about.
Features should be coordinated with the JIT, not the interpreter,
anyhow.
A normal user shouldn't change this, as it will slow down the emulation and can lead to bugs or crashes. The renaming is done in order to prevent users from leaving this on without a way to turn it off from the UI.