The level of coaches & umpires

[_MIA_]

Yes not just with fielding. Fewer walks, fewer swings at balls, more first pitch strikes, and hitting the easy pitches. Also not to discount you can do both.
But to assume they would be better causing a higher win % does not understand 186000 games.

You showed that errors are more common than what you think he was assuming and that not making as many leads to more wins. You said nothing about his point that making exceptional plays is more important than not making errors unless your 2) was showing that. If it was I apologize, I am not really a huge sabermerics guy.