It is safer to just put in the space (much like you put in the quotes to be safe). Python's argparse will also accept but not require an `=` separator (maybe optparse, too - I haven't checked that one).
It's only "safer" because argp has this particular bug. It's safer for argp (or python's argument parser, for that matter) to not have surprising buggy features like this.
While it may go against your personal expectations, I believe at least the Python variant is intentional not an accidental/unintended "bug".
"Surprise" is observer-relative. From a blank slate, if --long=val and --long val both work, then why not -s=val and -sval and -s val for a short -s?
So, I think the right word here is "disagreement" (perhaps about "which consistency - history vs. internal"), not throwing shade by simply declaring/asserting it a "bug".
