The situation is even worse

My test Code:
$app = Factory::getApplication();
print_r($app->input->get->getArray());

URL in browser:
../administrator/index.php?option=com_test&a=int

Result:
Array ( [option] => com_test [a] => 0 )

URL in browser:
../administrator/index.php?option=com_test&a=bool

Result:
Array ( [option] => com_test [a] => 1 )

URL in browser:
../administrator/index.php?option=com_test&a=attributes

An error has occurred.

0 Joomla\Filter\InputFilter::cleanAttributes(): Argument #1 ($attrSet) must be of type array, string given, called in C:\OSPanel\home\j6\libraries\vendor\joomla\filter\src\InputFilter.php on line 248

Joomla 5 code
protected function getArrayRecursive(array $vars = [], $datasource = null, $defaultFilter = 'unknown', $recursion = false)
{
if (empty($vars) && \is_null($datasource)) {
$vars = $this->data;
} else {
if (!$recursion) {
$defaultFilter = null;
}
}

    $results = [];

    foreach ($vars as $k => $v) {
        if (\is_array($v)) {
            if (\is_null($datasource)) {
                $results[$k] = $this->getArrayRecursive($v, $this->get($k, null, 'array'), $defaultFilter, true);
            } else {
                $results[$k] = $this->getArrayRecursive($v, $datasource[$k], $defaultFilter, true);
            }
        } else {
            $filter = $defaultFilter ?? $v;

            if (\is_null($datasource)) {
                $results[$k] = $this->get($k, null, $filter);
            } elseif (isset($datasource[$k])) {
                $results[$k] = $this->filter->clean($datasource[$k], $filter);
            } else {
                $results[$k] = $this->filter->clean(null, $filter);
            }
        }
    }

    return $results;
}

Joomla 6 code

public function getArray(array $vars = [], $datasource = null)
{
if (empty($vars) && $datasource === null) {
$vars = $this->data;
}

    $results = [];

    foreach ($vars as $k => $v) {
        if (\is_array($v)) {
            if ($datasource === null) {
                $results[$k] = $this->getArray($v, $this->get($k, null, 'array'));
            } else {
                $results[$k] = $this->getArray($v, $datasource[$k]);
            }
        } else {
            if ($datasource === null) {
                $results[$k] = $this->get($k, null, $v);
            } elseif (isset($datasource[$k])) {
                $results[$k] = $this->filter->clean($datasource[$k], $v);
            } else {
                $results[$k] = $this->filter->clean(null, $v);
            }
        }
    }

    return $results;
}

Bug in code

$results[$k] = $this->get($k, null, $filter);

changed to:

$results[$k] = $this->get($k, null, $v);