I don't know if it's explained more in the article, but IMO it would have been better if more explanation of the ranking process was given. It would have been better if the total number of votes for each pianist was given because if a candidate received a very small number of votes it doesn't seem of much significance.
I think an interesting question about a list like this would be "What would be the most effective way of getting the most meaningful list?" More votes for each pianist who voted? Some kind of ranked choice like they used in the New York City mayoral election? Having person voting rank their choices? A larger number of pianists doing the voting? Some minimum number of notes required to make the list? I don't know the answer to any of these questions but maybe someone with greater understanding of statistics can offer their opinion.
This list has appeared in some previous years in this magazine, and it would be interesting to compare the lists over the years.