You're making a fundamental error here... You're finding the start date for the plane in real life, then applying it to a specific version. Example, *WE* have a SpitV that has +16 boost, which is a much later version than the first ever spitV. You didn't see spitVs with +16 that early, that's for sure.
Example: You state the date of the E-4, but the nearly identical E-3 was in service before that date, for some time (E-3/4 have been considered the same plane by everyone everywhere), so that date isn't necessarily valid when comparing to others.
See what I'm saying?