It's an interesting idea, but it raises the reasonable (IMHO) question, "Why would they bother?"
It seems like an awfully big investment of resources for actions which wouldn't be of real benefit to them.
The theory has catchy name, but even the earth's nature disproves it.
I feel like a lot of so-called solutions to the Fermi paradox fail when they speculate on what "aliens" would do. Would they seal us off and make a zoo, or find it morally wrong to contact us, etc, etc. It's bold to assume a single policy, since there would likely be multiple alien civilizations, or multiple factions even if there is only one.
So I give this one more credit in that once you have reached 100% understanding of physics, you will know whether this premise true or not true and it more or less dictates that you answer it if it is true. However, I'm not convinced that with 100% knowledge of physics you would find yourself so vulnerable. And even if you were, it still seems various forms of containment would be just as effective as a genocidal attack.
This one kind of works because it only takes one civilisation to block us and keep the others out.
> once you have reached 100% understanding of physics, you will know whether this premise true or not true
How does understanding physics give you the certainty?
As a solution to the paradox that would assume that all civilisations are extremely xenophobic and also always assume that collaboration is impossible.
BTW: my current belief is that most likely life is just super-rare (phosphorus problem, and way too many required variables) and also that colonising a galaxy is probably a sub-optimal solution for overpopulation.
Applied to a forest on earth, you'd have to make the animals are extremely slow.