Updating customer entities without setting increment ID?

[mobweb]

Currently I am using the following update data to update existing customer entities:

$importData[] = array(
    '_website' => $websiteId,
    'email' => $emailAddress,
    'group_id' => $customerGroupId,
);

As you can see, we are only updating the customer group ID.

However, when using this data to update the customer entities, the "increment_id" field is set to NULL upon import.

Is there a way to update a single field (e.g. "group_id") without having to set the "increment_id" field?