The article states that Flora brand vegan butter has 80% butterfat. How can it be vegan if it contains butterfat?

I'm with you, OP! Vegan "butter" does not contain butterfat. It obviously contains some sort of fat, but it is not a dairy product fat. Peanut butter, almond butter and vegan butters should be using the term "fat" not butterfat.

ForA butter is vegan because it's made with cocoa butter not dairy butter. Note that there are other plant based products that use the word butter. Here in the USA, peanut butter is one such popular product.