Sometimes the simplest explanation is the right one...
We have played four games and we have received to open every one. Which means we have kicked off to start the second half each time. More possessions in the 1st quarter --> more chances to score, and vice versa for the 3rd.
That's a good point, but that still doesn't explain a discrepancy of 42-3 vs. 3-13.
Here's a look at 3Q scoring for each game-
Ohio begins 3Q vs Idaho with 15pt lead, up 28-13.
15:00 Idaho- 5 plays, 13yds, PUNT.
12:03 Ohio- 7 plays, 45yds, FG.
9:01 Idaho- 11 plays, 35yds, DOWNS.
5:49 Ohio- 10 plays, 45yds, MISSED FG.
Ohio begins 3Q vs Marshall with 7pt lead, up 14-7.
15:00 Herd- 3 plays, 6yds, PUNT.
13:37 Ohio- 5 plays, 14yds, PUNT.
10:59 Herd- 6 plays, 19yds, FUMBLE.
8:46 Ohio- 5 plays, 15yds, PUNT.
6:16 Herd- 3 plays, 9yds, PUNT.
- Ohio fumbles punt, Herd recovers-
4:44 Herd- 4 plays, 0yds, FG.
3:44 Ohio- 3 plays, -3yds, PUNT
1:45 Herd- 4plays, 25yds, FUMBLE
Ohio begins 3Q vs SELA with 21pt lead, up 21-0.
15:00 SELA- 10 plays, 74yds, FUMBLE.
10:46 Ohio- 9 plays, 27yds, PUNT
6:11 SELA- 7 plays, 48yds, TOUCHDOWN.
4:15 Ohio- 4 plays, 48yds, PUNT.
Ohio begins 3Q vs Minn tied 14-14.
15:00 Minn- 8 plays, 31yds, FG.
10:25 Ohio- 12 plays, 32yds, PUNT.
4:16 Minn- 9 plays, 42yds, PUNT.
I didn't include drives that started in the 3Q but finished in the 4th because the core would be applied to the 4th Q.