The strongest person at your gym and in the country are still part of the same reality. Thus this argument is meaningless.
Alright, the strongest person in my gym (located in the USA) vs. the strongest person in
Russia. They are now completely different and completely unaffected by each other, which is practically the same thing as different realities.
More significant means more important, but it doesn't mean the guy from the gym isn't the strongest in the country, there's no proof offered of that.
There's no 100% certainty, but there is a 99.9999% certainty that the guy in my gym isn't going to be stronger than the strongest man in Russia.