C-Script has a JIT ("just in time") compiler.
It is compiling on startup, where all those dots in the startup window pop up.

Lite-C also features a JIT compiler, it is running every time you run your game in debug mode.
But it also allows pre compiling, and according to jcl this will result in faster code execution.
In this case you don't have to deliver the source code with the finished game as it is the case for C-Script without using resources.

Most likely they are leaving away certain optimizations for the JIT compiler to keep the startup speed acceptable.

Still I think that the speed of the language is not the most critical point.
Whenever I had problems with the frame rate it was because of level/object rendering. Personally I never ran into a problem where a script was too slow.
Bad coding which performs poorly can be done in every language.
Back to the example Pathfinding: Why is it so slow? Well you have a lot of linked lists, but the slowest thing are all the traces for obstacle detection. And this is an engine function, not a script issue.