I can't imagine that doing this will result in more than a few drips being gained. I would not worry about it and enjoy my Fumoto valve.
If you removed the Fumitomo valve completely...would more than an additional tablespoon of oil come out? I agree we may be over-thinking this...but it makes a great forum topic that could explode into 40 pages.
Oh wait...someone already started a multi-page thread on this topic on bobistheoilguy website: huge Fumitomo thread
View my fuel log 2015 Mirage ES 1.2 manual: 51.8 mpg (US) ... 22.0 km/L ... 4.5 L/100 km ... 62.2 mpg (Imp)
I've thought about removing the valve and see what has been asked in thread. When I change my oil I have my front tires on about 4" blocks. I like using my mechanic creeper, & I need a little extra space to slide under the car. I feel the angle of my car may help the oil drain to the valve a little better & leave less in the engine oil pan.
I think this is a legitimate question or concern. Removing the valve with every oil change eliminates the advantage of using it, however. It may be worth doing sometimes, however? Then again, it may be only a very small amount not worth worrying about, too?