The only argument I could see for the need of these terms in addition to just light/ERM would be the ability to detect the existence of something beyond the furthest edges of the universe from where light reaches us through phenomena such as gravitational pull from beyond the edges on the bodies at the edges.
That light is the earliest light we can observe, but it is not the earliest event to have had casual effects on us, nor is the earliest event we can observe.
In particular, that light was emitted about 370,000 years after the Big Bang, while events within the first second after the Big Bang have had casual effects on us.
So there is an important difference between "light" and "casual" in physics.
Unfortunately I’m now just sort of stuck thinking about causality, determinism and free will...not exactly knowing where you are on Earth I guess it’s a possibility you have never been and never will in my light cone, yet my comment was the causality of your reply in some sense. And in maybe an HN 1st you’ve made me reconsider my position, and Recognize I need to more deeply consider causality as having good use outside phenomena from outside light at the edges of space and time and spacetime.
Causality refers to the underlying constraints from the theory (nothing travels faster than the speed of light), this is more general than talking about any particular type of particle/field.
The observable universe is the set of points from which information can reach you. That is not the same as spacetime?