I could be way off but I think I'm on target a low pitch rate causes more esters as they are a by product of the growth phase and a low pitch rate can also cause off flavors.
Take another look at the info from Clayton Cone and Neva Parker in this thread. There's persuasive evidence that higher pitch rates create more esters.
Just a FYI I read the links and it actually supports what I wrote about low pitch rates creating higher ester production though I was wrong abut the fusel alcohol which I thought was created with higher pitching rates. I copied the article and will paste below
Effect of Pitch Rate on Beer Flavor
Pitch rates, in addition to strain, temperature, and gravity, make a dramatic difference in the final flavor and aroma profile of any beer. The pitch rate will have a direct effect on the amount of cell growth during a fermentation. Cell growth decreases as pitch rates increase. Ester production is directly related to yeast growth as are most other flavor and aroma compounds.
A low pitch rate can lead to: •Excess levels of diacetyl
•Increase in higher/fusel alcohol formation
•Increase in ester formation
•Increase in volatile sulfur compounds
•High terminal gravities
•Increased risk of infection
High pitch rates can lead to: •Very low ester production
•Very fast fermentations
•Thin or lacking body/mouthfeel
•Autolysis (Yeasty flavors due to lysing of cells)