I’m glad that you are smarter then all the dozens or hundreds of professional astronomers in the world who have observed the object with wonder and open minds - unlike you - and not dismissed it out of hand.
What would science do if every one approached things with a closed mind and dismissed everything as something ordinary? Would they ever learn anything? Likely not. And they would would they go on social media and places like FR and demonstrate to all just how truly close minded they are?
I am sorry, I should have been more clear, and shouldn’t have been so defensive. I was not objecting to your explanation. The reasoning I read was different. Some astromoners, from studying the Kiuper Belt, and observations of nearby sun-like stars, reasoned that the solar system is passing through debris ejected from nearby solar systems. The made a rough estimate of the number and sizes of the members of that population of such matter within the orbit of Neptune.
It appears you are saying that another possible view is that given the number and size of such objects we have observed one can make a similar rough estimate of the population. From your tone, it appears that you object to such speculation. I do not, provided that it is clearly labeled as “speculation” a.k.a an “educated guess”. So long as the guesser does not demand billions of taxpayer dollars to verify his guess because “Science”.