Indeed. In interpreted REBOL languages, parentheses have extra storage and runtime evaluation costs, but in compiled Meta code, they are optimised away, so they cost nothing.

versus implementation issue mostly.

As always there is another point in arithmetic order. If we have an expression like 3ab + 2cd we do not mean to add 2 to the 3 * a * b first and only after that go and multiply our result by c and then by d. But I consider this a mathematics (lazy in notation and avoiding parenthesis)