This thread is a delight to read to get everyone's takes on definitions for "full set" and qualifiers and everything. It came up a couple times, but I'm curious to hear what the takes are for a "full 2600 set" or even a "full 2600 retail set," knowing it's close to impossible to narrow down due to the vast amount of one-off games and mail order exclusives and "basement-made" games.
If you count name changes as unique, then I think you would count it. Personally, since this is the same game just with new box art and name, I would say it's a variant.
Also, I feel your pain on defining a good set of rules for every release on every console. I think the Atari 2600 has broken me completely.