Output is 2.5 as expected. Of course for your specific example you'll use a local function and access the [1] index of the array. Rest is still the same.

SORT ()’s array argument is the entire FILTER () function. The sort_index value of 2 sorts by the Value column, the second column in array. The sort_index value is -1, which applies a descending ...

If you study the code, the two averaging functions, average2x and averagethird, are almost the same. The only difference is the one point where the math is different. Now look at this version.