Imo, I live by the "when in Rome do as the Romans do." You cannot push your morals on others but you can have a higher standard for yourself. My other qualm is that a 16 year old in that world is more mature than a majority 20 year olds in our world.
That proverb refers to customs which aren't really the issue here. Also, "not pushing morals" can easily be abused to become a catch all excuse to do nothing, even though you could. In fact, it has been in this story. Remember early on when they just began reconstruction? The MC learned about how the lord planned to make use of slave labour for the fields. Even said lord realized how that might upset him and offered to find an alternative. The MC gave him to go ahead with the original plan, due to this very mindset. At that point he was in a position to even abolish slavery on that territory at least, or at least insist on establishing more humanitarian standards for it. Nope, not a peep.
What I'm getting at is that "doing as the Romans" is not the point here - historical events must be considered against historical context. IRL the low age of adulthood was needed due to the harshness of life, pretty much constant warfare and the way the upper society worked. One can probably say that the same applies here, so of course he won't be going around telling them to change that. That does not mean that he himself shouldn't at least point the issue out: "where I come from, you're young enough to still be considered a child".
The age of the body is one factor, but I do think mental maturity is more important
Gotta be honest, dude - that came out creepy AF

I think a cryptobro once said somethin similar when asked what the age of consent's going to be in his future crypto-founded, government-free micro state
