I'm not sure if this is a bug, or a "wanted feature"

I observed amule 2.1.3's behaviour in the last weeks, and seems that often the first or top 2-3 clients on the queue get skipped from clients when a slot become available.
Let me make an example.
I'm watching the upload window (I find that relaxing

) and I see the uploaded data to a client is nearing 10Mb.
I'm curious to see who's next so I switch to the queue and see client A on top (QR: 1), then client B (QR: 2) then client C (QR: 3), then client D (QR: 4). There is enough difference in their score so they won't change their ranking in the remaining few seconds. To be sure, I also refresh the score list to make sure there isn't a client below, with higher score.
Client A is definitaly a candidate to enter the upload window.
I go then back to the upload window and after few seconds, one slot becomes available. I expect client A to take it... instead, often is client C or client D, or even clients sitting even more below.
This doesn't happen once, but several times, then I get bored to watch and leave amule alone... yet I don't find this correct.
Am I missing something or this is not the wanted behaviour? ?(