Extra Base Hit Rates between ATB 18 and 19

Mike N and I had a conversation over email that may be interesting to a wider audience.

Question:  Given that the 1906 era changes so much about the game, why do we see errors increasing at incredible rates, but we do not see Home Runs being reduced at expected rates?

Long Winded Answer: 
Fielding is binary, ball hit to fielder, fielder gets a "roll of the dice" so to speak, and the outcome is a catch or an error.  I assume it is easy to program this.  And over a long enough period of the time, the fielding percentages match what is expected for the combination of era and fielder quality.

Increase the error rate in an era, the DMB game engine can simply increase the errors in sim play.

The batting/pitching results are not binary - so much more has to go into the calculation.  On every pitch they have to consider the batter/pitcher matchup, the park, the fielding, the dozen or so player ratings, the weather, etc.

What is more important to the game engine - maintaining 70 HR's from Mark McGwire, or the home run rate in the dead ball era?  The engine has to thread that fine line - how much does it suppress great hitting from other era's?  I don't know how they exactly do this.

Add in the fact that every darn hitter we use is elite (plus every pitcher) and I think the engine just makes a bunch of judgement calls.

I found some old files from ATB 18 to compare certain stats.  It is a fair comparison I think, since we are using the same general player population and the only variable is the different eras.   Only concern I see is that ATB 19 is only has 5 or 6 weeks of data.

Here are stats on an at bat basis, a HR every X amount of AB type of thing
          ATB19    ATB18    % DIff
HR         50        41       -18%
3B         56       171       +67%
2B         50        20       +60%
K           8         6       +25%

To make sure we understand the first line, ATB 19 sees home runs every 50 at bats, while last ATB season, home runs were more prolific, coming at a rate of 1 every 41 at bats.

My unconfirmed conclusion is that the 1906 era is having a profound effect on ATB, but less so for Home Runs than other stats. 

As mentioned, I do think throwing only all time greats into a single league can wreak havoc on any era we choose.  I also believe this is why some of our all time favorite players just don't stack up well - Bob Gibson, Sandy Koufax, Albert Pujols, etc.