All Exceptional Set Items now drop with the maximum number of sockets. This means that your Set items with 3 Attributes and 2 or 3 Magic Affixes will always have 3 sockets!
It’s possible to get exceptional items that have just 2 attributes.
Two attribute exceptionals are not guaranteed to have 3 sockets.
How many attributes did they have?
Can you show a screenshot of a 3 attribute set item that does not have 3 sockets?