BUG Type 1
A grid of nothing but two-candidate cells would have two solutions. The one cell left with three candidates takes its spare digit.
How it works on this board
Removing the extra 2 would leave a two-candidate BUG with two solutions
8
4
1
9
6
6
5
8
1
9
3
1
9
7
8
2
4
9
7
8
3
6
4
2
3
5
7
1
9
8
4
6
1
9
8
7
1
2
4
8
9
5
7
5
9
3
7
2
8
6
7
8
6
9
4
3
1
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