^ It's possible, but given the complete absence of even an intimation that Cap w/IG was stabilizing the alternate Earth so he could bring more power to bear on it as a focal point of his power, unsupported. The absence of proof isn't proof of absence, but Hickman spent an entire issue with people talking around a table explaining the mechanics behind the Incursions. He wasn't exactly left wanting for panel space.
Furthermore, Reed's exposition makes it unlikely. "That earth is like an island breaking the surface of an ocean. He's literally pushing an entire Universe hidden from us..." Reed would have been the perfect person to have noted or advised Cap that he can't just push the Earth away, he has to reinforce it along with his efforts to push it otherwise it'd break under the strain. But all we see is the Earth and Reed, in no uncertain terms says, pushing the Earth is literally pushing its entire universe.
Finally, there are already strange physics at play during the Incursions. The proximity of those Earths being even that close together would have caused gravitic and atmospheric catastrophes. They didn't. Hickman goes out of his way to note that. Certainly, if they did, the IG would presumably be powerful enough to stabilize all those catastrophic forces. But Hickman set up the Incursions such that it was all but unnecessary. The crisis isn't: we have to push the Earth along with its universe away, but y'know, the Earth's mass cannot support a universe, so we have to also compensate for stress fractures along its crust, solid matter compression, gravimetric chaos anomalies, blahblahblah, etc. Indeed, those concerns are largely done away with already by Hickman.
The focus is on the Earth. Its destruction, or mutually assured destruction. The impossible choice. And the theme of New Avengers.