Each factory produced parts from their own designs, leading to interchangeability issues, until they all adopted the P14* standard. There are actually 4 main manufactured models of P14s, P14W, P14R, P14E, and P14*. The letter following the designation was the factory that manufactured it (i.e. W was Winchester, R was Remington, and E was Eddystone).
This is only referring to the manufactured models, not those updated to things like Weedon standard.
Nearly all is exchangeable, AFAIK only very early Winchester P.14 rifles had non-interchangeable parts with other manufacturers (what was also the reason for officially chosing only the Winchester rifle for sniper useage).
I remember when the UKintroduced the spike bayonet the question arose, whether this bayonet was capable of penetrating a German
winter coat - and that was still in officially peaceful times. So to claim that noone wanted war and everyone was thinking of peace by disarming might not be that correct.