This is such a typical question regardless of the size of your business. Multiple systems in place each one of them has customer data who should own the customer?
ERP - of course they control the billing information which is critical to the business.
CRM - why else would we have a CRM in place if we aren't mastering customer data from here?
Data Warehouse - let us gather all of the information from all the systems and master it here.
Why in today's technical world and landscape should one system master the data of an entity?
Architects should be changing the conversation to be focused on what information is critical to a particular system. Every system needs to hold customer data and locking a customer to a single system hamstrings your business processes. If we only let ERP create and master customer data, how do we get new customers and prospects in CRM? Are we back to paper forms? Don't laugh I have seen this happen with larger enterprise clients.
If ERP has to own the billing information let them, lock those fields down in the CRM once the prospect is turned to a customer. Make sure you give your sales and service teams the flexibility to manage the customer and related data. While your integrations might need a little more time to setup but your data warehouse will be all the better for it as will the overall view of your customer. By mastering information and not an entity you can be sure that your data is in sync and that you have an accurate view of your customer information.
Architects change the conversation, don't spin in circles trying to figure out who owns the customer, find out who needs what data and unlock the business processes to work for all.