There’s no such thing as internal customers.
A client is someone who pays in exchange for a service/product.
A client is considered one who can make your business profitable via their money.
For a business to be profitable (and create impact), it needs to be exclusive: to focus on the group that can build profit and exclude the ones who don’t (for a bad fit, incapability to satisfy their needs, not enough acquisition power, etc.)
And the most important thing about a client/customer and a provider relationship: the capacity to say no.
Can the “internal” client say no to your offerings?
Can you say no and withhold your offerings to an internal client?