My personal pet theory is this: That by getting to an OCU, you are given enough rope to hang yourself with: if you fail, in their retarded brains you've proved you can't cope with a multi-engine OCU..... so chop him! But get chopped before an OCU, and guess what, you're still under PTC rules and budgets = more chance of a restream.
Not strictly true. Sevewral years ago I was chopped on a rotary OCU, and was given a Multis Slot. The person before me who was chopped on said ocu (and was a bit of a muppet) got binned. However the person before him was good and got a slot on Multis. I grant you the climate several years ago was not as it is now but 2 out of 3 restreamed suggests that merit has something to do with the decision.