Author here, this is a valid point but there are also valid reasons to choose C structures. The larger framework that this is a part of is primarily targeted towards people working in cybersecurity, not software engineers. Cybersecurity people are very often not great software engineers and there is a high throughput of “throwaway” scripts, or “make a quick hacky change”. C is commonly already well understood, a bespoke DSL usually is not and requires a learning step. You can “hit the ground running”, so to say.

And, as a bonus, creating, say, a filesystem implementation is now often as easy as copy/pasting existing C structure definitions, either from the original source (which is usually C) or from reversing tools such as IDA/Ghidra.

There’s no right or wrong way in my opinion, just preferences.