As someone that has some experience in the Theravada side of things I will say that within modern Theravada circles I don't think many would speak of the conditioned as springing forth from the unconditioned.
On the comments about it having Annihilationism there is some discussion there but I think that misses the point too.
Ajahn Thanissaro has written some excellent works on this.
I am going to post some quotes here for the concept of Nibbana within the Theravada/Pali tradition.
I think Mahayana deepened and expanded the understandings in some ways (If one looks at Mahayana positive) with really delving into Emptiness, Same as it did with Dependent Origination to Non-Arising, Same as it did with many other subjects.
Mahayana is about becoming Buddhas. Theravada is about becoming an Arahant. Nothing wrong with either Lol, though Buddha's are referred to as the Blessed Ones for a reason
Samsara as Nirvana I think can be seen in the Pali Canon it just was never talked about with this language.
The Pali Canon is a systematic text to become awakened. It isn't exploring the "leaves of the forest" or going into subtle language and poetic understandings.
It is literally a systematic text of instructions to become awakened.
Once the Blessed One was staying at Kosambi in the simsapa forest. Then, picking up a few simsapa leaves with his hand, he asked the monks, "What do you think, monks: Which are more numerous, the few simsapa leaves in my hand or those overhead in the simsapa forest?"
"The leaves in the hand of the Blessed One are few in number, lord. Those overhead in the simsapa forest are more numerous."
"In the same way, monks, those things that I have known with direct knowledge but have not taught are far more numerous [than what I have taught]. And why haven't I taught them? Because they are not connected with the goal, do not relate to the rudiments of the holy life, and do not lead to disenchantment, to dispassion, to cessation, to calm, to direct knowledge, to self-awakening, to Unbinding. That is why I have not taught them.
"And what have I taught? 'This is stress... This is the origination of stress... This is the cessation of stress... This is the path of practice leading to the cessation of stress': This is what I have taught. And why have I taught these things? Because they are connected with the goal, relate to the rudiments of the holy life, and lead to disenchantment, to dispassion, to cessation, to calm, to direct knowledge, to self-awakening, to Unbinding. This is why I have taught them.
"Therefore your duty is the contemplation, 'This is stress... This is the origination of stress... This is the cessation of stress.' Your duty is the contemplation, 'This is the path of practice leading to the cessation of stress.'"
"This is peace, this is exquisite — the resolution of all fabrications, the relinquishment of all acquisitions, the ending of craving; dispassion; cessation; Nibbana."
There's no fire like passion,
no loss like anger,
no pain like the aggregates,
no ease other than peace.
Hunger: the foremost illness.
Fabrications: the foremost pain.
For one knowing this truth
as it actually is,
is the foremost ease.
Freedom from illness: the foremost good fortune.
Contentment: the foremost wealth.
Trust: the foremost kinship.
Unbinding: the foremost ease.
"There is that dimension where there is neither earth, nor water, nor fire, nor wind; neither dimension of the infinitude of space, nor dimension of the infinitude of consciousness, nor dimension of nothingness, nor dimension of neither perception nor non-perception; neither this world, nor the next world, nor sun, nor moon. And there, I say, there is neither coming, nor going, nor stasis; neither passing away nor arising: without stance, without foundation, without support [mental object]. This, just this, is the end of stress."
"There is, monks, an unborn — unbecome — unmade — unfabricated. If there were not that unborn — unbecome — unmade — unfabricated, there would not be the case that emancipation from the born — become — made — fabricated would be discerned. But precisely because there is an unborn — unbecome — unmade — unfabricated, emancipation from the born — become — made — fabricated is discerned."
Where water, earth, fire, & wind have no footing:
There the stars do not shine,
the sun is not visible,
the moon does not appear,
darkness is not found.
And when a sage,
a brahman through sagacity,
has known [this] for himself,
then from form & formless,
from bliss & pain,
he is freed.
"Birth is ended, the holy life fulfilled, the task done. There is nothing further for this world."
Some are born in the human womb,
evildoers in hell,
those on the good course go
while those without effluent: