...that's it?
That doesn't seem like anything to me, actually. "Across time and space, one heart." That doesn't imply there's only one Arceus in the multiverse. Universe? Absolutely. But there's no mention of anything else.
Not to mention you can get multiple event Arceuses on the same cartridge, or other Pokemon there should be explicitly one of without trading.
What
are we counting events as, by the way? Canon? Not canon? It's being used as evidence for the Ash-Greninja debacle (there was an Ash's Pikachu in HGSS, if I recall as well), but we don't count event-only moves on profiles. Case in point,
Magikarp: Celebrate and Happy Hour are nowhere to be seen, and neither is
Rayquaza's V-Create event.