It's a wildcard. Passing in any other variable name would ideally raise an error about the use of an undeclared variable or a mismatched type. The use of a wildcard disposes of those errors.
> the mispelled name problem is really no different than what you might experience today
Not quite; your modified examples includes two declarations on their own lines. Being on their own line gives them greater visual presence at-a-glance than the new syntax which buries the declarations within a parameter list.
Worth noting is that my trivial example managed to confuse at least one reader who was unable to see the issue.
> All declarations are explicit.
While true, you've muddied the lines a little by moving declarations into the syntax of other expressions. Where previously a declaration sat on its own line or at the beginning of an assignment, they may now be peppered throughout the syntax in ways that are not so easy to observe at-a-glance.