Pilots were probably required on both vessels. Lots of traffic. I could see a scenario where the pilot departing the pier thought he was making starboard to starboard passing arrangements but was in contact with a different vessel.
I am a lot in the Kiel Canal. In Kiel Canal for this size of ship it is compulsory not only to take a pilot but also professional helmsmen (people who have a OOW 500 GT licence and and who take over the steering for the entire canal passage). General practise for ships of this size is that the master goes down below during the canal transit and leaves the OOW with the pilot. As a rule during the canal passage the pilot has the con even though officially the OOW of the vessel remains in charge. However this is not always easy as the conversation between pilot and those helmsmen as well as with all coastal parties and other ships is entirely in German language. This can cause a severe delay until the OOW realizes that something is going terribly wrong and until he might call the captain to inform him about this…