The only way I can think of to validate the 'distinct count' feature in workspace would be, if you have a dimension that can identify a single visitor (ID) and then make a visitor based segment using distinct count.
1) in workspace use the segment which has distinct count 2) filter such that you only see one visitor using your ID dimension 3) breakdown the visitor using the dimension for which you based your distinct count on
I would then expect the report to show the distinct values for that visitor and the count should match what is set in your segment.
But then the 2nd question will have no answer, as following screen capture gives:
The segment is set to:
Then, a table is created, I tried to breakdown 1 product ID by same dimension, but I cannot get "What other Product IDs are visited as well - if a visit viewed PROD500001".