Precession only occurs the direction of a gyro's axis is being changed. The discussion is about trimming in straight & level flight: no yaw, no pitch rate, therefore no precession, therefore no right (or left) wing rise
But, but. A gyro maintains its rigidity with respect to space. An aircraft traveling at a not inconsiderable speed (400+ knots) is constantly pitching with respect to space (6.7°/hour with respect to the earth, the actual rate with respect to space depends on ones track) ie the gyros (engines) axis of rotation is being changed. Whether this has any relevance to aircraft handling behavior I leave to others.