Game Full of Vacuum and Air Look the Same?

The argument goes like this:

Delving deeper, from The Book we see the leadoff hitter receives roughly 4.80 PAs per game and the 5th hitter only receives 4.34. Over 150 games, that means that the leadoff hitter receives roughly 70 more plate appearances. Over these 70 plate appearances, the amount of runs gained by switching a player from the #5 spot to the #1 spot who is 20 points of wOBA better is roughly one run. This may be erased by properly leveraging an on-base threat at the top of the lineup, but it certainly will not end up being significant to the point of a win or likely not even half a win.

I have a difficult time fully believing it. I haven't read the details of the simulations but it seems to me like we're looking at the situation in at least somewhat of a vacuum. I can think of several effects that make it important for a good hitter to be batting at the top of a lineup (in addition to having the most atbats).

1. Puts starter in stretch: It's tougher physically to pitch from the stretch, the more time a pitcher spends doing this during a game, the better for the opposing team.

2. Starter has to deal with baserunners: It's tougher mentally to pitch with a runner at first since there's simply more to think about, any amount of focus that is taken away from the hitter at the plate has to be positive for the opposing team. In the case of a big stolen base threat at first they're also going to draw more pickoff throws and possibly more fastballs/pitchouts to the batter at the plate.

3. More pitches (short term): A pitcher who just threw 15 pitches to get out the 1 and 2 hitters is going to more tired while facing the middle of the order than one who got them out with 8 pitches.

4. More pitches (long term): Having the guys who see the most pitches bat the most often is going to get the opposing starter's pitch count up faster and get them out of the game. Also, the more pitches the opposing team sees, the better to time them.

I don't think any of these effects is huge (since the difference between a good/bad obp and pitches/plate appearance are both only about 15%), but they must make the lineup order somewhat more important than just considering total number of atbats it will produce, so some quantifiable effect is being missed in the fangraphs analysis. Anecdotally, Ricky Henderson having a 10 pitch atbat to lead off the game and then robbing the pitcher's attention has got to put that team in a much better position to win the game than someone making a quick out. I would like to find out how much of a difference this really all makes.