That narrative is just plain wrong. Remington wasn't involved in development for one. By mistake or on purpose the AMU sent Remington the the "match" or "wylde" chamber print rather than the "NATO" version. Remington just took what they got to SAAMI.

This accounted for a very small amount of the difference between pressure tested loads and the wildcat velocity claims. The majority was simply handloading to higher pressure than intended. This has been proven in ballistics labs.