Don`t worry about it as it`s probably just your rear seal leaking on the shaft once you get the car going .... just kidding !!!
I have the Tilton unit on mine and I haven`t seen this yet . Aren`t you in South FL ? Could the humidity cause some flash rust on the sleeve that gets polished off as the clutch is used ?
When I assembled mine , I put a THIN coat of white lithium grease on the sleeve .
Bob