I've simmed the '74 season several times this afternoon. Setting H&R to Very Low has not made any difference that I can see.
I should add, too, that IRL the NL and AL had identical league ERAs. The BA in the AL was 3 points higher than the NL. When I sim the '74 season, the NL almost always has the higher league ERA -- often .20 higher. That is rather surprising, isn't it?