If the codebase is small and owned by a few people then it might be true. But when the codebase gets large enough and worked on by multiple teams - it is unreasonable to expect that everyone will understand the workings of the whole application.

So why did they invite you to the interview in the first place if you are not diverse enough?

I didn't disclose my race because getting a job should not be about the color of my skin but my merit.