'Maintain' 15 degrees suggests he could suss attitude, and that 15 was what he wanted. That also happened post Roll issues, no? Given that he may have selected TOGA, is it possible he was comfortable with a) 15 is acceptable, the a/c is Stall protected, or b) he was flying "g pants".
Maintain is the key word, for it suggests that however he sussed the flight path, his Pitch was 'appropriate', in his opinion. He also may not have been aware of the value.