Limiting attributes returned for on v1 SOAP API

Despite the SOAP documentation seemingly always showing v1 and v2 being the same with the exception of how you call a method and there being a ton of example of v2 calls. I cannot seem to get this to work in v1 of the SOAP API

$attributes = new stdclass();
$attributes->attributes = array('price');
$attributes->additional_attributes = array('special_price');

$result = $mageConn2->catalogProductInfo($session2, $sku, null, $attributes, "sku"); // works as expected

$result = $mageConn1->call($session1, '', array($sku, null, $attributes, "sku")); // returns all attributes

I’ve tried all variations (I feel) and have had some luck in limiting the return to basic values, just not the ones I’ve requested.

How should I be calling a v1 SOAP API to limit the returned attributes.

NB: I’m using v1 because of the multiCall method as this is ultimately used for a product sync.

Thanks In Advance