Order.create - registering multiple Participants (participantPayment records not created properly)

Creating an Order to register two (or more) participants creates two (or more) ParticipantPayment records, one for each participant line item, registering two participants via an Event page creates only one ParticipantPayment record regardless of the number of participants registered.

Which is the correct one/what is expected behaviour?

Steps to reproduce

Call Order.create with parameters similar to:

$params = [
  'total_amount' => 100.00,
  'financial_type_id' => 4,
  'contribution_status_id' => 'Pending',
  'payment_instrument_id' => 1,
  'currency' => 'USD',
  'source' => 'Multiple participants (Order.create)',
  'contact_id' => 2,
  'line_items' => [
    1 => [
      'line_item' => [
        0 => [
          'price_field_id' => 3,
          'label' => 'Tickets',
          'financial_type_id' => 4,
          'price_field_value_id' => 3,
          'qty' => 1,
          'field_title' => '1 Ticket',
          'unit_price' => 50.000000000,
          'line_total' => 50,
          'entity_table' => 'civicrm_participant',
        ],
      ],
      'params' => [
        'contact_id' => 2,
        'event_id' => 1,
        'role_id' => 1,
        'source' => 'Multiple participants (Order.create)',
        'price_set_id' => 7,
        'fee_level' => '1 Ticket',
        'fee_amount' => 50,
      ],
    ],
    2 => [
      'line_item' => [
        0 => [
          'price_field_id' => 3,
          'label' => 'Tickets',
          'financial_type_id' => 4,
          'price_field_value_id' => 3,
          'qty' => 1,
          'field_title' => '1 Ticket',
          'unit_price' => 50.000000000,
          'line_total' => 50,
          'entity_table' => 'civicrm_participant',
        ],
      ],
      'params' => [
        'contact_id' => 5,
        'event_id' => 1,
        'role_id' => 1,
        'source' => 'Multiple participants (Order.create)',
        'price_set_id' => 7,
        'fee_level' => '1 Ticket',
        'fee_amount' => 50,
      ],
    ],
  ],
];

$order = civicrm_api3('Order', 'create', $params);

This results in two ParticipantPayment records:

// civicrm_participant_payment
[
  {
    "id": 5,
    "participant_id": 5,
    "contribution_id": 18
  },
  {
    "id": 6,
    "participant_id": 6,
    "contribution_id": 18
  }
]

Registering two or more participants via an Event page, always creates one ParticipantPayment regardless of the number of participants registered.

// civicrm_participant_payment
{
  "id": 7,
  "participant_id": 7,
  "contribution_id": 19
}