Ok...I think I got my answer. Eligius is actually 2 separate pools (US and EU). Payouts aren't shared, but the "top miners" for whatever reason (as well as total pool hash rates) are lumped together. It looks like the math works out if only looking at US or EU miners...
Yes, that's right. US and EU payouts are completely independent. I made the "top miners" shared because it made more sense. In my opinion, having two of them for each server would look weird and confusing (and make it harder to compare !).