I wouldn't think that the oil level in the tank would have much effect on the amount of oil in the crankcase of a dry sump engine. If it is being correctly scavenged back to the tank there should be very little oil in the crankcase.
Yes in a regular dry sump engine the crank case runs at a depression, so not only is there very little oil but the seal is stopping higher pressure air from the outside being pulled in. Only when the engine is stopped (or has a serious issue) do the seals stop oil wanting to get out. Also when the engine is off you can (on some designs) drain past the oil pump gears and fill the sump. Therefore it wouldn't be a surprise to see a little weep only when left standing.
