Having two possible logical answers to one of those pattern questions is quite stupid. The student is not wrong to select the other one then, is he?
Actually there are multiple possible answers to any PTM question. In fact, since you only have 5 images to work with, you could theoretically justify any of the 120 possible combinations as being a sequence. The idea here is NOT that there will only ever be one correct sequence (no there will be 60 justifiable sequences in every question, - 120 each way).
The idea here is that there will be ONE sequence that is much more obvious and clear and one that makes much more direct sense than any of the other sequences. There is a hierarchy in the UMAT where the simpler pattern, should one exist, will always trump a more convoluted and ambiguous pattern to be the correct one.