There might be a reason it was never fixed. Something stupid like a lot of 30 year old scripts relying on this out come. Hope not, you're right that error message is ass
Wow, that is an unhelpful error message. It could have told you it was expecting a number. It turns out that -i is short for "interval" and expects a number, whereas -I is used to specify an interface.
It’s actually a technical term in language theory – a term that cannot be produced by the language, but is still considered part of the ‘universe’ (i.e., the set of all terms) is called ‘garbage’ or ‘junk’.
Since I can’t find a source online to verify this claim, this might just have been the case in my courses…
"Invalid" or "unparseable" are more understandable descriptors in normal language. I don't think I ever heard of garbage/junk being used for that in language theory but it may be domain specific usage.