I'll start by saying there are very few instances where using a 650A rim will help with brake reach vs. 650B. There's only a 3mm difference in radius between the two.
650A was very popular in Japan and East Asia for many decades on both utility bikes and the lightweight randonneur and camping bikes inspired by the French constructeurs that were popular in Japan in the 70s, 80s, and 90s. Japanese industry offered lightweight 650A rims and tires during this time period for cyclotourists, and still do. While 650B is taking over as the dominant size in this category in Japan, you will find that many touring bikes of the last 50 years were built for 650A.