So I was reading this article, and it got me thinking about this question. If particles remain entangled at a quantum level regardless of distance, and this phenomenon may be related to wormholes, that could explain how Sparks might return to the AllSpark regardless of distance across space, or the AllSpark being removed from the Well for most of the war! I think when a Spark is created, it is quantum paired to the AllSpark of which it is essentially always a part, and remains so regardless of time and distance. We know that Sparks have both a mystical/spiritual and physical aspect - they are a form of energy that can be manipulated using physical means, like Shockwave did with Trypticon and its crew. I have always thought that Vector Sigma was a quantum computer as well. Perhaps parts of Spark twins’ Sparks are also quantum paired, so they have that link which seems to function regardless of distance.
Sparks have a physical element, so how does physical energy move across unknown distances of space back to the AllSpark? What guides it? Isn’t it limited by the speed of light, and if so, wouldn’t Sparks from the far reaches of the war not return until hundreds of thousands of years after the person died? But what if the quantum entanglement of Sparks and the AllSpark allowed Sparks to get back via subspace, or basically wormholes! That is why it’s in their nature to return, and also why they can’t be seen traveling back. Perhaps the Cybertronian body, with its mass shifting, subspaces, etc, (gifts from Vector Prime), has enough space-time weirdness built in to maintain the Spark during life (the Spark in fact determines the form of the body, including all of that), but in death those effects fade and the Spark returns to the AllSpark. It just boops back instantly (best technobabble ever). Perhaps the Spark chamber itself is a kind of space-time vessel, similar to the Reliquary the AllSpark was hidden in.
So how does Dark Energon prevent something as basic as quantum pairing from working? It’s actually very spooky! Unicron is the Chaos Bringer, so his essence might nullify or disrupt the natural physical properties of things down to the quantum level, even supersymmetry! The unholy and unnatural mystical aspects of Unicron’s corruption separating people from Primus have a corresponding physical aspect as well, since everything about Sparks is both mystical and physical.
Another interesting thing to consider is the artifact of Onyx Prime, the Tryptic Mask, that allows the wearer to see the Spark’s journey after death. It may be some kind of quantum computer as well, whose link with Primus and nature allows it to accurately determine some of the normally undeterminable aspects of quantum mechanics. Perhaps it lets you see the wormholes at work, but Onyx was so in tune with creation, life, and death that he understood them intuitively just like he was looking at them. Ooh! What if it could even determine what is needed to get rid of the influence of Unicron over a Spark!
So anyway, yeah. Sparks can always return to the AllSpark no matter how far apart they are, because quantum entanglement is not affected by distance, and can probably cause/is the same thing as wormholes.