That sounds pretty close to correct. But the problem isn't so much that
Arguments are two non-terminals. In fact, note that the actual supplemental syntax there is
CallMemberExpression, which is only one non-terminal.
I'd put it more like this: there's a context that could equally well be the start of a
AsyncErrorFunction, and (in the absence of
CallExpression is expecting
AsyncArrowFunction is expecting
and attempting to handle those two possibilities will quickly lead to conflicts (i.e., points where the two possibilities will 'tell' the parser to do something different). And yes, those two possibilities can be distinguished by a following
=> (or lack thereof), but that's arbitrarily far away, so unless your parser has unbounded lookahead, it's stuck.
(That's assuming it's a deterministic parser. A non-deterministic parser wouldn't care about any of the above.)