My DD had a substitution on her WISC and it seemed to make sense to me, although it doesn't really matter. She would have qualified for DYS without the substitution and didn't need the higher score for any reason.
I don't remember the details, but the tester wrote a paragraph explaining the reason for the substitution. Apparently DD correctly completed all of the block design and was able to solve all of them, but went very slowly and carefully. So the report described her score with the time limit and then that she was able to complete it when given more time. She then had a substitution for that part. The resulting score was almost identical to her score on other tests, so it seemed reasonable to me - but, again, it didn't matter that much as we had all of the scores on the report and it was easy to see exactly what had been done.
I did once have a tester who adjusted my daughter's score on a test to help her get a higher score. That really bothered me and I never used the score from that test. My daughter had met the termination criteria for missing questions, but was allowed to keep going and then given points for the additional questions. I was unhappy about that. So I'm sure cherry picking does happen, unfortunately.
