This is actually much more common than you probably realize, there are statistics that show that many men well into their 20s are still completely sexually inexperienced, which is a trend that has been growing over the years. Not having been in a relationship by 30 is not the norm but there may be a wide range of reasons for it.
I'm 31 and only had a handful of sexual experiences and dated a bit but never been in a relationship, and I'm a white male that is 6'4" and athletically built. I put literally 0 effort into this when I was a teenager. In my early 20s I had a really traumatic and humiliating experience that completely ruined this for me and I didn't even approach or ask a woman out until I was around 27. From 27 to 29 I had a lot of really bad experiences that were leaving me exhausted and in a place where my mental health was beginning to suffer, so I totally stopped and focused on other things. The trend for me was this, I was chronically having bad experiences that were creating stress in my life to the point where it was better for me to totally walk away and focus on other things. I'm really happy with my life right now and have a ton of amazing things going for me, both in the present and in the medium to long term for the future.
Today's dating market sucks and I truly believe that there is something very wrong with many women today, not all of them but enough where it is causing issues. If a guy like me has a hard time I can only imagine what it's like for an average man.
For this man, he never should disclose information like this to a woman, as it will just lead to auto rejection and from there will encourage a continual spiral of him getting rejected, giving up, etc.