The task isn’t arbitrary. It’s designed to measure mental ability. And it’s not boring as it can be quite short. And the rules should be quite easy to understand as they involve things like “which shapes fit together.”
The test is not designed to be confusing or hard to understand.
I expect IQ is also correlated with being a white collar drone (pretty awesome) but it’s also correlated with whatever intelligence is, as imperfectly as we’ve defined it.
The tasks which can be reduced to finite integer sequences are absolutely arbitrary.
E.g. you're given a finite set of pictures and expected to guess what the next picture is from a few possibilities. The answer is that it's all of them since any finite sequence has an infinite number of generating functions. The only way to get it right is to try and read the mind of whoever wrote the test and guess what they meant. An invaluable skill to have in the white collar workforce when guessing what your boss actually wants from you. But white collar empathy is not intelligence.
The test is not designed to be confusing or hard to understand.
I expect IQ is also correlated with being a white collar drone (pretty awesome) but it’s also correlated with whatever intelligence is, as imperfectly as we’ve defined it.