You haven't come off as trying to sound like a know it all. GAM does all of our hatching so I don't know either but I have seen humidities all over the charts. Some folks are successful...some are not. I think it depends on the type of incubator. I know she says she runs much lower humidity than some people but we have a big cabinet and hatch chickens, ducks, turkeys and geese all at the same time.
I say if it works for you and your hatches are successful...Just do it.
If you have some Turkey eggs and duck eggs when we come down I'd like to get just a few, not too many, I have heard when a duck hatches it looks like butter coming out of the shell, so I'm just curious and I have never hatched these before. So maybe just 3 of each and can you put them in the bator at the same time?