Hi Iamsmart!
I have to be honest, I've heard about this before but never studied it. So I took a few snapshots of drive-byes this morning to take a look and the results were... surprising.
Prediction
Having a large acre count results in a smaller income, therefore we will see fewer seeds per acre at higher acre counts than lower acre counts.
Method
Take a drive-by of the same target two ticks in a row, take the seed difference, and then calculate the number of seeds harvested by a single acre.
Results - Summer
Trees:
6 acres yields 623 seeds per acre.
275 acres yields 622 seeds per acre.
11,374 acres yields 622 seeds per acre.
17,293 acres yields 622 seeds per acre.
Bush:
8 acres yields 1,990 seeds per acre.
203 acres yields 1,990 seeds per acre.
19,755 acres yields 1,990 seeds per acre.
31,182 acres yields 1,990 seeds per acre.
Flower:
6 acres yields 11,605 seeds per acre.
16 acres yields 11,604 seeds per acre.
3,038 acres yields 11,604 seeds per acre.
4,552 acres yields 11,604 seeds per acre.
Grass:
6 acres yields 19,893 seeds per acre.
16 acres yields 19,892 seeds per acre.
2,788 acres yields 19,892 seeds per acre.
3,927 acres yields 19,892 seeds per acre.
Conclusion
There is no detectable decrease in the number of seeds produced per acre for higher acre counts. Therefore - there is no reduced income for higher acre counts O.O
Further Work
If someone count independently verify these results then awesome. I haven't tested if you grow less for higher acre counts than usual, but I suspect not.