The description examples are different from the actual test cases:

Description

knight_to_h3(["f4"]) => False

knight_to_h3(["f5"]) => True

Test Cases

test.assert_equals(knight_to_h3(["f4"]), True)
test.assert_equals(knight_to_h3(["f5"]), False)

If by "real world problems" you mean clients that make confusing statements, then yes, I agree.

The description is confusing. There are two almost equal statements: decrease of 1.5 percent and increases of 0.5 percent. However, from the examples, they mean different things. First one is taking a percent of the values, second one is just an addition to the percent.

I labeled it as an issue, but looking at this discussion, I guess nobody is going to fix that.

Nice kata, but it requires some math knowledge (even though it's a very simple one). Probably 6 kyu is a better option just because of math?

Any discrete math course covers sequences. This one in particular is an arithmetic sequence.
I suggest to study discrete math as it often helps to find O(1) solutions to different problems like combinatorics, sequences etc.