Boeing does not "plead" flap30 for all approaches.
The forward view is improved in low vis conditions by using flap40.
Flap30 is normally only used if the aircraft is operated under JAR OPS and there is an issue with approach climb weight due to operations with DA below 200`.
In addition, if the aircraft is a fail operational 737 600-900 certified for CatIIIb ops, then flap30 is the only option if you plan to land with one engine operating.
And you will be amazed by the number of people who should know what they are talking, and it turns out, they do not.
Ask him for the Boeing reference, I`m sure Boeing Flight Ops would be surprised if he can give you one!
