Well, in my opinion.
Across when referring to movement over a distance means 'from one end to the other' without any further context, across the road, across the river etc
I mean, if anyone has an issue with it being literal, then the burden of proof is on them to say so, if anyone thinks it's from one galaxy to another, again, burden is on them to prove so
Gas was stated to fly across the universe in a distance too far for one IT trip, if there's proof that this statement is not literal or it means he flew within a galaxy or any other assumption, they just be proven, taking the statement as it is provides the least amount of assumption. Saying "it could be this or that" is not a reason to ignore Occam razor
They didn't say across a galaxy
They didn't say across galaxies
They said across the universe
It's like a statement saying someone went across the planet earth, and then one starts saying it could mean from a city to the next in one country, or one country to the next in the same continent, and even this would pale to this particular case