In software development, new builds are typically rolled out in "waves" and each wave is bigger in size than the last but requires more automated metrics to be successful before moving up.
For example, you may want to roll out a new build of Facebook, what you would do is roll this out a few thousand people and wait until the success rate of http requests is high enough to move onto the next wave and so on. This ensures that obvious bugs are caught early and rarer bugs that only occur in the 0.1% of cases are caught before it hits everybody.
Tesla most likely have a similar concept of waves except the members of each wave are based on diversity in the pool. You may get some people who drive lots, or some people that charge frequently at super chargers or people that use NoAP a lot. This way, each wave has the highest possibility of catching bugs before progressing onto the next wave as the diversity is as high as possible.
Depending on the severity of the bug, a particular software version can be halted at its current wave and then superseded by a new build. This would mean that those on a certain version would get prioritised over others.
So this is just a long winded way of saying that its not likely to be a simple case of 'FSD' owners getting builds earlier than others, its just a pattern we seem to observe given the strategy of rollouts.