Surely in a situation like this the British would come out to destroy Tirpitz?
Enigma decodes would give the game away.
Would Bismarks crew willingly fire on another German ship? Even in Red October Remius didn't seek battle to defect, his posture was defensive in the face of being attacked by Soviet forces. On a surface ship the crew would have a clearer picture of what was happening, the opposition would not be invisible.
''Give me a Ping and one Ping only'' - Sean Connery.