I haven't seen this in writing anywhere, but I think the deal is you have to be first team all district to be considered for all region. Every one of the Dominion boys you see above, whether for first or second team or honorable mention all region, was a first team All Dominion District selection. I don't see any of our second teamers. Also there is no effort to "correct oversights" or perceived slights; you don't see kids passed over at the district level resurrected at the regional level.
This can lead to some anomalies, because let's face it, the talent in some districts is deeper than in others. There are only 7 teams in the Capital District, for example, and two of them are hapless, so that's only 5 teams' worth of players vying for all district honors. In contrast, there are 7 strong teams in the Dominion and I think at least that many in the Colonial. (Meaning no slight to the Central, I just don't know those teams as well.)
But what you see is, someone gets 2nd team all district and gets no consideration for all region at all, while someone from a weaker district gets all region. I know my own son missed some games with an injury and thus lost his chance at first team all district, hence no all region consideration. Cest la vie.
Bottom line, if you're going to do it at all, you have to have some sort of process and rules, and any way you do it, you'll end up with arguable situations, allegations of "politics", etc. The kids named above all had great years, they deserve recognition, I would leave it at that. I don't feel like my boy got cheated and I would hope others would leave it alone also.
I have seen other districts where they name more boys and have only one all district team, not first and second team. I have seen several districts who name 4 first team pitchers, in particular. All of that is just tweaking. Where ever you draw the line, someone will be just above it, someone will be just below it, and someone will want to argue with you about the final decisions.