Jarno,
I’m sure you’re right, but why not use dithering when it actually increases resolution and hence gives you a better quality file (even if you and I can’t hear it)? On the other hand, I always try to avoid extra processing (dithering in this case) if I can help it and keep the highest resolution until the end. Then I don’t have to worry about any of this. But if for whatever reason I have to lower the resolution at some point, then it gives me peace of mind to dither. If that doesn’t bother you, then good for you 
Take care!