Everybody that enters the country for the Olympics is subject to the Olympic Bubble....this is not limited ot the Olympic Village, but at every holding camp around the country and also at every hotel that anyone related to the teams is staying at....you are not allowed to mix with the general public. You are escorted from the hotel to the bus, and from the bus to the training venue. You have exclusive floors of the hotel, if not an exclusive hotel where nobody can enter. You cannot go shopping or out for a coffee, unless it is an exlusive coffee shop such as the one connected to my hotel in Tokyo.
The idea is to contain any positive covid tests within the bubble and protect the largely unvaccinated Japanese population. It does not matter to the Japanese Government if an athlete tests positive and has to sit out the Games, or anyone he has been hanging out with has to spend some days in isolation.....they just do not want it to impact on the Japanese public, 80% of whom did not want these games in the middle of a pandemic, with people from 206 different countries, many of which are developing new strains of the virus that is impacting on a 3rd or 4th wave, that the Japanese are trying to avoid. If someone brings the virus in to the Village, they will not let it get out without a fight, even if that means putting the whole US team into isolation.
If the US Team has come in 14 days ago, the Sam could have been negative after 5 consecutive days of negatibe tests and then been allowed to compete, just as the South African Soccer players were. The 7 British athletes end their 14 day isolation tomorrow and are all free to compete.