The only stipulation required for SA entry (minus USCGA) with regard to MOC (and other nominations) is that everyone needs to have one. MOCs are free to administer their selection process as they see fit.
To address some of the above, USMMA allows candidates to be nominated from any MOC in their state. I had ran into trouble with this during my cycle and most offices turned me away, but one office let me interview after I showed them the black and white. The MOC requesting an additional nom is most likely a function of your MOC trying their best to get you in. If you get in, you’re a happy constituent. You either got in off your MOC’s nom or the other one that was called in. Happy constituents = constituents who vote for you = re-election.
The same for the USMA issue. In states/districts where nominations are highly sought after, MOCs tend to be choosy in how they give out nominations. If they use a few slots on candidates who aren’t viable for whatever reason or they don’t want to go to that SA in the first place, then that nom can’t be used for a candidate who needs that nom and wants to go to thar SA. What that boils down to is that you have candidates who are possible appointees (potential happy constituents) blocked from that opportunity by a candidate who most likely won’t be going to the SA in question. Again, MOCs want to make as many candidates happy because that is their job and that’s how they stay in office.
Yes, there are candidates who get a lot of nominations (Rep and Senators for one SA, all 4 from one MOC, etc.). However, typically, those are candidates who are water walkers or SA nominations are less competitive. Also, SAF is most likely not the best sample since those who are on here as candidates are typically those who want to go to an SA the most because they are doing the research. People who are usually motivated to this degree have probably done their due diligence in all avenues of their life to make themselves as qualified as possible. SAF gives them a platform to share the fruits of their labor.
Nominations can sound like a heartless process when there is a lot of emotional skin in the game. Know that nominating authorities are out in the tough spot of having less nominations than candidates. I don’t envy them nor do I envy SA admissions departments. They have a tough job in finding America’s future cadets/MIDN amongst a very talented and qualified pool of applicants.