Just some food for thought. Can you consider the VDB's a variation since they changed the design later in the year? If it is considered a variation, then it is possible to have a complete regular set without the VDB's even though everyone considers them part of the set.
Interesting question....or is the VDB the standard, it was issued first, and the non-VDB the variation? Hmmm It may be the way it is today because someone in publishing decided to include a space for both in their collector albums. Just a guess.....
I think you need it for the set of Lincolns. It's the first Lincoln cent and the story around the removal of the initials is an interesting part of the now 100+ year history of the series. Now when they include the VDB coin in a U.S. Type set album, that's a little more questionable, but it seems to be accepted as a separate type design.
I strongly believe it is part of any 'set'. what I don't agree with is the inclusion of error coins as part of a set.
I second that thought. You will not complete a set of Lincolns without the VDB. It is not a variety nor an error, it is a mint issued circulation business strike coin.