You're making it sound like there were 2 independent engine projects going on separately and only coincidence they're both 3.5s. A 2nd gen 3.5 for the f150, and then a totally separate GT supercar 3.5 that was detuned for the Raptor. Sorry that's not how it works in that field.
There is one new 2nd generation 3.5 platform, that is then tweaked with several variations of it. The regular f150 baseline version, a tweaked raptor version, and an even further tweaked GT version. Still all the same 2nd gen 3.5 at heart, with varying levels of changes to it.
Also just because ford dropped the news in a certain sequence, doesn't mean that's the order they came about behind the scenes.....rather a sequence that is best for the press.
GT is announced with a new 3.5....WTF? Guess it's good if it's in a supercar
Raptor is announced with a new 3.5....WOW, the Raptor is getting a GT engine!
F150 is announced with a new 3.5....WOW, the f150 is getting a Raptor engine with a couple less ponies
vs.
F150 isannounced with a new 3.5....big whoop it's already got a 3.5 now
Raptor is announced with a new 3.5....big shoes to fill, it's just another f150 engine
GT is announced with a new 3.5....WTF they're putting an f150 engine in the GT?
See what I mean?
The Ford GT program started back in 2013. So it's pretty clear the order they announced the succession of motors/vehicles is correct.