People doing 10 units (2007)
100 UAI: 0%
99 UAI: 17%
98 UAI: 20%
97 UAI: 26%
96 UAI: 27%
Edit: Didn't read your last sentence of you already checking the UAC reports.
The stat suggests that the students with higher UAIs do more than 10 units. But determining causality is difficult. It is likely that the more academically able students complete more units, so it is not surprising that they gain higher UAIs. On the other hand, if students only study 10 units of UAI courses and do badly in one course, their UAIs will be depressed.
The data show that the better students (judging from Schol cert results) did, indeed, tend to study more units and within each group there was a tendency for students who studied more units to obtain higher UAIs. This does not, however, completely answer the question of causality. The relationship between number of units studied and UAI within each group might result from personal attributes including interest, motivation, effort and time management. You cannot assume that simply by studying more units, your UAI will be increased.