Thanks Simon, so it is agreed about the engine fill.
However, rather than to avoid unnecessary worry by customers, I suspect it is more about product liability.
On that subject, it is interesting that they state "Minimise contact with engine oil".
I think that it is to pass the onuses on to the end user with the problem with getting rid of the residual product, that is now in contact with the fresh oil.
The only method, I can think of, is carry out sacrificial oil changes to try to get rid of the stuff!