It doesn't make sense that they would take the level into consideration TWICE for to hit. (BAB and 1/2 to attribute)
Let's explore the other attribute option (1/3 rounded up):
Stats:
1, 2, 3 = +1
4, 5, 6 = +2
7, 8, 9 = +3
10, 11, 12 = +4
13, 14, 15 = +5
16, 17, 18 = +6
19, 20, 21 = +7
(I...