networking – When do I need a vendor OUI MAC?

I work in a company where we build our own devices that include a network interface. However, this interface is actually in a comercial device of a different vendor, i.e, our device includes a network device among other components. This network device has its own MAC address, provided by its vendor.
As a result, our device is identified by a MAC address that includes the OUI prefix of the network device vendor.

Is this appropriate? Or should we have our OUI prefix and overwrite our network device MAC with a MAC of our own range?

I have checked that some companies in our field have registered their own OUI prefix. They are also companies that manufacture devices with a network interface but do not manufacture network devices. Is this a common practice? Is it actually a commercial decision?