I'm a fan of trios, regardless of gender combinations (providing the males are neutered). I prefer trios because if one glider dies it isn't leaving a single glider behind.
Before i go on, please keep in mind this is my personal opinion, not a guarantee. Ultimately it's up to the gliders how it it will all play out.
All male (neutered) trio can work yes and thrive, but since they are neutered males you can also add a female so your gender options are wide open.
,but again it's up to the gliders, here's what i mean.....
Your current boys may accept the new male but the new male may not accept your boys or vice versa.
one of the 3 may not do well in a trio, some gliders do better in pairs and won't accept a 3rd (or more ) even though they are colony animals and you would think the more the merrier it isn't always the case.
but that doesn't necessarily mean the new glider will be the odd man out. One of the current pair may accept and like the new male and the new male reciprocates, while the 2nd of the current pair doesn't like the new one.... causing a shift for the bonded pair and giving you another decision to make.
Do you split the bonded pair leaving one single making a new bonded pair, or keep the bonded pair together and find another potential cage ,mate for the single new guy.
Now, it could also work out just fine with the 3 with no issues at all.
These are issues and possibilities we face when introducing gliders of any age or gender, they aren't specific to male only colonies.
I've got two cages that do great in bigger colonies ( one has 4 gliders and has 3, both cages lost a glider in the colony so it was 5 and 4) these cages will accept any glider I introduce, even if they are handicapped.
and then.......... I have one cage that does better as a pair. The pair was a trio, and was in a colony of 6 at one point, that colony failed and had to be broken down to 2 trios. The trio still wasn't working so I removed one of the females, ever since the pair have been doing great. I'd love them to be a trio but that isn't what they want.
Introduction issues can be a nightmare for people with one or two gliders because you always have the risk your going to still end up with a single glider and two cages so these things need to be considered before making the decision to add another.
For me it's no big deal, I have enough gliders between the 2 accepting cages that if an intro doesn't work out with one it likely will with the other. Worst case scenario for me is I pull one glider from an existing colony to pair with the single. People with one or two gliders don't have this option..
so your question " isn't it more natural for there to be 3 or more instead of 2"
is a hard one to answer. In hypothetical terms yes it'd be more natural, in reality it all comes down to the gliders involved.
Also bear in mind if the intro is successful and you have a new colony of 3 the roles each glider had previously is likely to change. The current dominant male may not remain the dominant glider one of the other two may take that role. A submissive glider can become dominant and vice versa