Just off the top of my head and as there are no replies...in a sense I think that is always what happens.
The true state of things includes ignorant aspect as well as informed aspect.
Knowing the state of things is also knowing the state of ignorant things.
So all nirmanakaya are seemingly ariseing from a spontaneous source and a ignorant source as well...to my way of thinking.
Both then being true.
Our linear consideration of these things are a part of the delusionary aspect as I see it.
Time is all relationship as well.
So that considered a present buddha is always and has always been a buddha as time is only relationship. A relatiionship changes not the things themselves in this manner of consideration.
So a bit complex seemingly, but I think it then be true both things from pure and impure considered states areise nirmanakaya.
Just off the top of my head...I could perhaps expound a bit or others could.
In a conventional sense........... looking at awakening as a uncovering process not a becoming other or added onto process. One is always this way just not knowing of it...when knowing produces nurmanakaya. Nirmanakaya however being always pesent in things of the real, in some manner shape or form. A process, a procedure of action. Circumsantially produces the presentation but always present as process in the way of things.
"This order considers that progress can be achieved more rapidly during a single month of self-transformation through terrifying conditions in rough terrain and in "the abode of harmful forces" than through meditating for a period of three years in towns and monasteries"....Takpo Tashi Namgyal.