Ya, it’s kind of legacy. If you’re using low LPB values and moderate/slow tempos you’ll hear the effect more distinctly, but if you’re running, say, 16 LPB patterns it’s definitely more of a “trill” as @Neuro_No_Neuro suggests
Might be better off creating a phrase with the musical relationship and pattern you would like the arpeggio to take, then playing it up and down the keys that way.