First, Bernard and Brian and not names which are alternatives one for the other.
I have checked Thomas and Shores book: "The Typhoon and Tempest Story" and W/O Calnan is recorded as a POW. However, given that he was shot down just a few weeks before the war's end, I suspect that there would have been a serious breakdown in the usual standards of administration in Germany. Whether Calnan was actually registered as a POW by the Germans and his details passed to the 'Protecting Power' I don't know. It might be that he was recorded as 'Missing' but retrieved by the allies from a hospital, rather than released from a POW camp - what does AIR 78/ say?
I would say that if he was in the enemy's custody, then he was a POW.