[coldtea]

>The number of bugs in a program correlates with the number of LoCs, but that's about it (correlation does not imply causation).

No, but it suggests it, and in this case, there's not many other options that could explain this than causation.

>The claim is also quite absurd, since, for example, you can pre-process any C or C++ program ever written into a single line of code, yet this operation doesn't reduce the number of bugs in these programs, therefore the amount of bugs is not "just" a function of the amount of LoC

That's an irrelevant strawman. When people speak of LoC they mean as to how many LoC are needed for various tasks based on the expressiveness of the language. Not whatever old LoC based on arbitrary adding needless lines (e.g. by preprocessing to inline function calls)...