Note the signature of Ll1 and the lack of conversion functions.
You are looking at the _old_ manual. That section is obsolete, but I did not have time to go through the whole manual again.
That said, ECL no longer implements unboxed functions. It was very hard to maintained and lead to code bloat: we had to provide two functions for every signature, one with Common Lisp objects, another one with unboxed values. It could be reimplemented using appropriate proclamations, but the default action was to remove it.
Outside from function arguments, the rest can be fully unboxed, as you see in the new code body, which is also more readable.