A data file is less expressive than code. Oddly enough, this can be an advantage, if you want to get things "right." There's a theorem in Computer Science called Rice's Theorem. It states that it is impossible to prove whether a semantic property is true for any arbitrary program. A semantic property describes what it does like "does it halt?" as opposed to syntactic properties like "does it have 'if' statements?" Most things people care about are semantic properties.
This means that if anybody questions whether your program is "right," it's a real challenge. You can't answer that in general, so you first have to demonstrate that your program is not just any arbitrary program - it has particular traits that let you answer some semantic properties about it. In your case, it would be things like "Is this rogue ability implemented properly."
Data files are less expressive than a Turing complete language, so it is typically much easier to demonstrate semantic properties like "correctness." I'm working on an application right now that chose to model a particular behavior as a state machine and a file of "constants" because we found it easier to prove the behaviors we care about from those two data-file inputs.
It's a balance. The less expressive the format, the easier it is to prove statements about it, but the less it can actually describe. Hardcoding is just one extreme end of that spectrum, with maximum expressiveness and minimal provability. Speaking in vague generalities, many programs find that some aspects are best described using a data file while others are better expressed via hardcoding.
There's two disadvantages to consider for datafiles:
- One has to define the engine that parses the files and acts upon them. This can be a challenging piece of code.
- When determining if any code change is valid, one has to consider any possible data file that could be provided, while if everything is hardcoded, one typically only has to prove that that one version works.
Data files should be leveraged when neither of those is a driving factor.