The only reason that people say levels don’t matter is because the animal welfare sizes are set for how far a piggy should be able to run from one end to the other end of his cage.
For example, Rabbits should be able to do at least 3 hops from one side of it’s hutch to another, and if you were rescuing one this would be a requirement, you couldn’t turn around and say, ‘it can only do one hop from one side to the other but theres three levels so thats three hops’ because thats not the point, there should be one level that at least meets the minimum,
You can’t put a dog in a two story kennel thats too small on either of the two floors, but say if you added the top level to the size it would fit because there would be 10 square foot all together if you add the two 5 foot levels together.
Guinea pigs aren’t made for climbing and alot of two storey cages/hutches are made more for the owners benefits of space saving than the animals, yes it’s fine to have upper levels etc. But only if you still have a minimum size on the base for the pigs to run, they tend to enjoy running in circles and doing laps of their cage.
Also, bungalows may have less square foot, but whats the point in an old woman having a two storey house if she can’t get up the stairs ?
I’d say keep your pigs the way they are as long as they can talk to each other, i’ve never had two boars that have fought in the past come back together after, this shared area arrangement is less stressful for all involved