Considering the fact that the system itself stated that this was merely a theory, Lex did not yet take this as true, but he had to admit it explained a lot. If all modern energies and beings were made 'efficient' for better use of resources by the universe itself, but all 'Primordial' beings were basically all-purpose, that would explain the 'weight' Lex felt his body exerted on the Midnight Realm.
It wasn't actual weight - although there was a lot of that. It was just that ever since he embarked on the path of becoming a Primordial, laws would need to exert more energy to process his existence, and would suffer a greater strain from interacting with him. Of course, this also made it that Lex had an easier time manipulating laws when he needed to.
In fact, it made so much sense that Lex had to keep reminding himself that this was just a theory so far. It certainly provided a logical explanation for why systems were able to break their rules.
