[intro.execution] p8 Sequenced before and the subexpressions thereof

Consider this example

   int a[2][3] = {{0,1,2},{3,4,5}};
   int i = 0;
   auto r = a[i++][i++];

[expr.sub] p1 says

The postfix-expression and the initialization of the object parameter of any applicable subscript operator function is sequenced before each expression in the expression-list and also before any default argument.

In this example, a is sequenced before the first i++, and the a[i++] is sequenced before the second i++. [intro.execution] p8 says

An expression X is said to be sequenced before an expression Y if every value computation and every side effect associated with the expression X is sequenced before every value computation and every side effect associated with the expression Y.

Do these two rules guarantee the side effect of the first i++(which is the subexpression of a[i++]) is sequenced before the value computation of the second i++? The meaning of the "associated with" is not clear enough here.

Improvement

An expression X is said to be sequenced before an expression Y if every value computation and every side effect associated with the expression X is sequenced before every value computation and every side effect associated with the expression Y (including these of the subexpressions thereof, if any).

With this improvement, the side effect of the subexpressions is ascribed to the evaluation of the post-expression.

Start by reading [intro.execution] p8 and [expr.sub] p1 in the draft, then trace how the wording applies to the nested subscript expressions in the example. Done means resolving the meaning of “associated with” and, if needed, updating the standard wording to make the intended sequencing explicit.