Putting the (very valid) reasons for not having human-readable game saves aside, are you sure it's worse than using a 3rd party library that's built to accept semi-valid input values, possibly evaluates user input in some way and has difficult to debug bugs that occur only under certain inputs? I agree that writing a stable and safe parser for a binary data file isn't easy, but there's less things that can go wrong when you can hardcode it to reject any remotely suspicious input. Third party XML/JSON libraries OTOH try to interpret as much as possible, even when the values are bogus. Also no need to deal with different text encoding bugs, line endings...
> Putting the (very valid) reasons for not having human-readable game saves aside,
I don't follow. What would the reasons be?
A human-readable game save file is presumably human-editable.