In my opinion, there are four possibilities:
1. the seller has shown the same stamp from the booklet twice instead of showing
two separate stamps - one from the souvenir sheet and one from the booklet.
2. the seller is attempting to sell the souvenir sheet stamp, but using the
wrong image, for a much higher price simply because it has been recalled,
and not because it is gummed instead of being self-adhesive. His use of the
word "error" or "variety" [I can't remember which word he put on the stamp].
refers to the "recall" not the gum.
3. it is a stamp that has been "gummed" after
Canada Post produced it, making
it a "fake".
4. it is a "gummed production" stamp that would be worth many dollars of
dollars.
Perhaps #2 is most reasonable, as:
#1 is, at worse, deceptive advertising;
#3 makes it a criminal act
and
#4 happening is virtually impossible.