Still guessing here.
It could be that the fact that you are using 'compare' => 'EXISTS' that 'type' => 'NUMERIC' is being ignored. But I really do not know.
Honestly I would expect your query to work. However, take a look at this https://stackoverflow.com/questions/43624283/orderby-and-order-not-working-for-numeric-meta-query
Note that the numeric values that this person wants to order by uses nested meta queries using both ‘>=’ and ‘<=’ comparison with no values so that it will return anything that has any value except an empty string or is non-existing.
