I'm not yet convinced that everyone is reading and interpreting Elon's tweet correctly. The trouble with Elon statements is that you have to be very careful how you read them as they may be true in a limited sense, but not in a less careful, more simple and straight forward reading sense. In this case, I could definitely see "we’re making our Supercharger network open to other EVs later this year" meaning that just 1 or 2 start-up EV makes was going to be able to use the supercharger network, not that all other EVs will be able to use it. I know I've seen
pics of an Aptera with a Tesla charging port, and their announced date for beginning deliveries is January 2022, which would track with the timeline in Elon's tweet.
I would have also included the possibility that he was only talking about a limit portion of the supercharger network, like only locations in a specific country or region. But a subsequent tweet from him said that it would eventually include the entire network, "
Over time, all countries."