Hi Albert,
As per my understanding, the system creates homogeneous storage units automaticallywhen the putaway takes place in a storage type that is managed for storage units. Therefore storage units will be created automatically only upon the creation of transfer order. A transfer order is not created during goods receipt, only a transfer requirement is created. So i doubt whether SU will be automatically created during Goods Receipt.
For more understanding on creation of storage units, please refer the below documentation link:
Creating Storage Units - Warehouse Management System (WMS) - SAP Library