EntityGenerate 'default_values' value not processed correctly when it's an array property

I ran into some problems when trying to set the format of a text field inside an entity_generate plugin.

...
            'default_values' => [
              'field_description/format' => 'basic_html',
              'field_specifications/format' => 'basic_html',
            ],
...

This wasn't working, which I thought was weird, since I could use array structure inside the 'values' configuration.

// Gather any static default values for properties/fields.
    if (isset($this->configuration['default_values']) && is_array($this->configuration['default_values'])) {
      foreach ($this->configuration['default_values'] as $key => $value) {
        $entity_values[$key] = $value;
      }
    }

So my previous example was being processed as:

'field_description/format' => 'basic_html',
'field_specifications/format' => 'basic_html',

Instead of the expected

'field_description' => [
  'format' => 'basic_html',
],
'field_specifications' => [
  'format' => 'basic_html',
],

It should be using the same logic as the 'value', using NestedArray and separating it by the property separator '/':

NestedArray::setValue($entity_values, explode(Row::PROPERTY_SEPARATOR, $key), $source_value, TRUE);