The drive on the FX track (which is set to zero as any other track) has absolutely no effect on the levels. Also there is no routing to the FX track anyways. I left it at just this one track specifically to rule out any summing issues that might occur.
I scanned the manual back and forth and there is no mentioning of that this is by design (as mentioned somewhere else in here). It’s rather sparse on the inner-daw out-routing itself.