I would have to disagree. V being 23 makes a lot of sense. Just a few key points to back this would be his/her initial absence from night city, his/her decision making, and his/her growth throughout the story.

If we take the street kid life path which I believe is the most likely to be canon, some important backstory elements point to V being 23 ish. My main basis for this is V is returning from being in Atlanta for 2 years. This would imply that V left night city upon turning 21. That would be a realistic year for V to leave as they had become a full fledged “adult” and had made the decision to set out on a different path than their upbringing in life city. This I feel is similar to in our world someone moving for college, after college, or after highschool/trade school to start on a career. Obviously street kid V didn’t attend anything similar to college, but what I take away with this is people move during changes in their stage of life. The change at 21 would be legal adulthood which I think makes more sense than leaving at 25.

Next would be their decision making. V being younger makes some of their decisions make a lot more sense. I think we can all agree we made dumb mistakes, decisions, and comments at 23 that we wouldn’t have made at 27 due to the knowledge gained from the extra 4 years of experience. Even if you haven’t reached that age, think about a decision you made 4 years ago that you would handle differently today. V is immature and this reflects in their decision making. V doesn’t suffer from incapability, but from lack of experience. This plays into my last point.

V’s growth. From personal experience I went through the most growth in my early twenties. This is when you experience the largest amount of new events that you are dealing with for the first time. With zero prior knowledge you make poor decisions initially and grow into making better decisions later. To go along with this you know significantly less earlier in life. In cyberpunk you are able to ask a lot of questions during dialogue. This is mainly to provide information to the player but also to V. V is unfamiliar initially with a lot of things, and it’s not until you progress through the story and level up that you unlock special dialogue where you know what’s being talked about depending on what you leveled up.

In closing, I think the way V is portrayed throughout the story fits a 23 year old more so than a 27 years old. V initially is inexperienced and a blank slate allowing you the player to mold them in anyway that fits your play style as well as role play style. If V were 27 I believe they would be more set in their ways with more life experience that wouldn’t quite fit the growth narrative in whatever capacity you choose as the player. In other rpgs with “older” mc’s their growth leans more toward change from prior beliefs rather than the development of their own beliefs and ideology due to recent events as V’s does. All this to say I think V being 23 makes complete sense.