It's a different case. The article you posted is about someone that has a high level of RH antibodies.
In the main article, the rare blood type is because the the A, B, AB, 0 and RH+/RH- groups are due to 3 antigens (2^3=8). But there are like 20 or 25 more antigens that your blood may or may not have, so there are like 2^23 or 2^28 blood types. Some are very rare, some combinations are very rare. Most of the time the other 20 antigens don't produce a reaction that is so strong [1], so for most transfusions it's enough to classify using the A, B, and RH.
[1] Why? I'd really like to know why, or if I'm oversimplifying too much.
In the main article, the rare blood type is because the the A, B, AB, 0 and RH+/RH- groups are due to 3 antigens (2^3=8). But there are like 20 or 25 more antigens that your blood may or may not have, so there are like 2^23 or 2^28 blood types. Some are very rare, some combinations are very rare. Most of the time the other 20 antigens don't produce a reaction that is so strong [1], so for most transfusions it's enough to classify using the A, B, and RH.
[1] Why? I'd really like to know why, or if I'm oversimplifying too much.