Obviously I don't know your product, but that just sounds like an endpoint that exposes a join table.

Any time I see status code sidestepping, it informs me that something more basic has been skipped earlier. "The monitoring is firing too often because of 404 errors, we should make this endpoint send back a 200 all the time so we stop being bothered by errors that are not errors" reads to me like curing a symptom.