Yes, I can see why he feels snubbed! But I agree: unless there's something more than just hurt feelings involved, he really shouldn't say anything.
I had something similar happen when I left my old company, and I DID say something to HR. Because in a way, it was an HR matter. My company sort of forced me out by playing games with me, changing my duties, changing my hours; essentially changing/eliminating the position that I was in. I'd been there over 9 years by that point. They said it was a 'resource issue', but I could see through that. My wonderful coworkers took me out for a last lunch, and I appreciated that. But on my last day, NONE of my supervisors or managers, past or present, came by to wish me well. NOBODY talked to me regarding my departure, what I was working on or anything. HR didn't come by to give me anything relating to end-of-employment materials, or about how long I would have computer or building access. When my normal departure time came, I just walked out the door with the rest of my personal belongings and that was it.
I composed a message to HR, expressing my disappointment that despite my 9 years of service to the company with consistent good reviews, I didn't hear anything from even one person in HR or management about my leaving. Not one 'we wish you the best' or anything. From a security standpoint, nobody even stopped by to make sure I surrendered my security badge. I set the email for delayed delivery, for about 5 minutes after I walked out of the door, so I was gone by the time it was delivered. Of course, this is the company that fought my unemployment claim (and won....darn this state). During my going-away lunch, even my coworkers were incredulous that no supervisors or HR had spoken to me yet, about anything, even security issues. (Normally, employees were escorted out the door when they left, and for some, they were told to leave immediately when they gave notice.)
(In retrospect, I guess I shouldn't have been surprised after what happened with my birthday several years earlier. Over the years, I was asked to sign so many birthday cards for coworkers. There was always some mention of a person's birthday, possibly even cubicle decorations or a big sign, even if the birthday person took the actual birthday off or it fell on a weekend. When my birthday rolled around this one year, I got....nothing. No mention. (My actual birthday was on a day that I normally had off, so I thought they would do something the day before.) I was kind of bummed. Then I remembered that the bowling outing was that weekend (the day after my bday), so I thought maybe they were saving the surprise for the bowling outing. Nope; we just bowled. Let me tell you, I didn't even want to sign the darn card when the next birthday rolled around, especially when it was for a person who was rude, grumpy and ill-mannered a lot of the time, unless she was trying to suck up to someone (and supervisors never did anything about it).)