It is unexpected relative to the 5s, but it is also rare in your sample, meaning that its occurrence in the sample is in exact proportion to how often you'd exp

It is unexpected relative to the 5s, but it is also rare in your sample, meaning that its occurrence in the sample is in exact proportion to how often you'd expect it to occur, given the distribution you inferred from your sample. That means you have no grounds for singling it out as "abnormal."