You're right on that — those trying to get into pilot training, as opposed to those who are already qualified, operational military pilots, are assessed IAW two completely different standards.
The US forces, for instance, all used to require 20/20 uncorrected on the first exam for pilot applicants. The Army started allowing 20/50 for commissioned pilot candidates back in the 1960's but demanded 20/20 for warrant-officer candidates until only a year ago.
As of now, the USAF and US Army have set 20/50 correctable to 20/20 as their basic requirement for entry into flight school, yet both allow 20/400 correctable to 20/20 after one is qualified. The Navy still maintains a more anal-retentive set of rules.