[Admins]

There are a few things that are incompatible between the two scripting engines, which make it sometimes look more strict. The main problem are variables like "this.x". While in the new scripting engine you can access everything in an object-oriented manner, meaning "this." could be replaced by "thiso." if not inside a with-clause, by other objects or be removed if you just want to access variables of the object the script is running for, in the old engine it was a special construct which only redirects to the dynamic (non-built-in) scripting variables of the npc the script is running for.
I wouldn't say the new scripting engine is more strict though, it's just not running 100% of the old scripts in exactly the same way the old engine would do it. The new scripting engine is also about more than just a different syntax description, it is also running scripts in a more optimized way, allowing scripts running other scripts, allowing the C++ engine to directly call script functions and doing something with the return values, is producing byte code so that the data sent to clients is smaller and needs less processing power and less updates on the client.