I agree; I don't think BQN values terseness more than k. I think k values terseness a lot.
I think it may be more convenient to write terse code in BQN over k, because there is greater facility to control function calls in a terse way. Things like under and over are quite common patterns that BQN finds easier (and shorter) than k.
I've not spent a great deal of time yet with BQN, so this could be wrong.