Using php null safe and null coalescing operators with an array containing anonymous functions

The following code works as expected:

$array = [];

// null
var_dump($array['foo']->bar ?? null);


// this throws a warning
var_dump($array['foo']?->bar);
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The null-coalescing operator supports array while the null-safe operator doesn't.

--

Lets take the following code:

function calculate($num1, $num2, $action)
{
    $actions = [
        "add" => function ($a, $b) {
            return $a + $b;
        },
        "substract" => function ($a, $b) {
            return $a - $b;
        },
        "multiply" => function ($a, $b) {
            return $a * $b;
        },
        "divide" => function ($a, $b) {
            return $a / $b;
        }
    ];

    return $actions[$action]($num1, $num2) ?? "Action forbidden";
}

// 1) int(3)
var_dump(calculate(1, 2, 'add'));

// 2) Warning: Undefined array key "addd"...
var_dump(calculate(1, 2, 'addd'));
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If I update the code with:

return $actions[$action] ?? "Action forbidden";
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Then it works as expected:

// 3) string(16) "Action forbidden"
var_dump(calculate(1, 2, 'addd'));
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Of course, if I update the code this way:

return array_key_exists($action, $actions) ? $actions[$action]($num1, $num2) : "Action forbidden";

// 4) string(16) "Action forbidden"
var_dump(calculate(1, 2, 'addd'));
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But it loses all the benefits of null-coalescing...

Question

Why I cannot use null-coalescing with the following format (or what am I missing?):

return $actions[$action]($num1, $num2) ?? "Action forbidden";
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