As a comment on Parcel, this is kind of a counter productive one. What's the utility of a comment that says "it can't do something, but I don't know what"? If you have the details, those are super valuable to comment with, but if you don't... why comment?
Because "there exist situations that parcel cannot handle because it doesn't allow configuration". That's a useful thing to know. The fact that the OP can't recall what the situation was also provides a useful piece of information; that it's likely something that is not run into often.
From what I read one of the developers wrote on here, Parcel does allow for configuration. It just doesn’t require it.
It’s actually convention over configuration taken to an extreme where it’ll start adding entries to packages.json for you, or wrapping rust code in WASM for you on import.