I think it is based on the fact that to be eligible for Oscar consideration, a film has to play commercially for two weeks in the Los Angeles area, during the nominee year

So Film Festival screenings are out

Members only or subscription screenings are out

Clip movies (like That's Entertainment) are ineligible, because they are mostly footage from earlier films

Films first shown on TV then released theatrically are also ineligible

That's why almost of all of the Oscar "push" films will be released in LA on or about December 13 or 14

Interesting bit - Charlie Chaplin's film Limelight (made in 1951), won an Oscar for the 1972 year. It was eligible because it had never before been screened in the Los Angeles area.

The rules for Documentaries and Animated Films are a bit more complicated, and I am not sure of the details these days

And yes, here in Australia, the Oscar nominees are screening now, or will be released in a couple of weeks, to coincide with the awards ceremony.