Return only two fields from the expression of the query record

if you query  record type then by default primary key of that record will be available as output along with your selected fields.

Then how you will identify that a given record data is associated to which record? As Gopal answered, it is available by default for that particular reason only.

There is no way/option to remove primary key from the queryRecordType() but you can manipulate the generated result by taking reference from below code.

a!forEach(
  a!queryRecordType(
    recordType: 'recordType!{aa4ce38f-1a9d-4827-af51-e2ccb80a2c8b}AS Vehicle',
    fields: {
      'recordType!{aa4ce38f-1a9d-4827-af51-e2ccb80a2c8b}AS Vehicle.fields.{7aa3dcda-863a-4271-9034-85821a2bd453}vehicleMake',
      'recordType!{aa4ce38f-1a9d-4827-af51-e2ccb80a2c8b}AS Vehicle.fields.{767a1f4c-ca0a-4df5-954d-cd0beba06e96}vehicleMileage'
    },
    filters: a!queryFilter(
      field: 'recordType!{aa4ce38f-1a9d-4827-af51-e2ccb80a2c8b}AS Vehicle.fields.{595da20e-a849-4c36-a57e-d569453c622f}vehicleId',
      operator: "in",
      value: {1,2,3,4}
    ),
    pagingInfo: a!pagingInfo(1, 10)
  ).data,
  'recordType!{aa4ce38f-1a9d-4827-af51-e2ccb80a2c8b}AS Vehicle'(
    'recordType!{aa4ce38f-1a9d-4827-af51-e2ccb80a2c8b}AS Vehicle.fields.{7aa3dcda-863a-4271-9034-85821a2bd453}vehicleMake': fv!item['recordType!{aa4ce38f-1a9d-4827-af51-e2ccb80a2c8b}AS Vehicle.fields.{7aa3dcda-863a-4271-9034-85821a2bd453}vehicleMake'],
    'recordType!{aa4ce38f-1a9d-4827-af51-e2ccb80a2c8b}AS Vehicle.fields.{767a1f4c-ca0a-4df5-954d-cd0beba06e96}vehicleMileage': fv!item['recordType!{aa4ce38f-1a9d-4827-af51-e2ccb80a2c8b}AS Vehicle.fields.{767a1f4c-ca0a-4df5-954d-cd0beba06e96}vehicleMileage']
  )
)

Does this result in an actual problem? Or is it just not what you expected?