> Have you ever noticed that lots of programming languages let you use parentheses to group operands, but none use them to ungroup them?

Since this doesn't exist in practice, shouldn't the article author first explain what they mean by that?

The examples at the end show that it's syntax for "parse such that this expression is not grouped". Essentially I guess this could be modelled as an operator `(_+_)` for every existing operator `_+_`, which has its binding precedence negated.