A lot of kids move around if they want to keep playing or they drop from the baseball program and just stay at the school if they like the school but aren't getting the baseball return for the time required.
It's very rare for any program, even a top notch WCAC school like PVI, to have a single graduating class where they send 7 players to D-1, including SEC, ACC, and other top schools, 1 walk on at ACC D-1, and 1 go to quality D-2.
These 2008 PVI guys all played on high achieving travel and school teams, and I assume they wanted to play at the highest level they could qualify for. They did get offers and the schools that offered must have done their due diligence.
Could some players have gone to lesser programs, including more to D-2 and D-3s, where those players would have had better chance to play right away? Sure. Would that college option have been better than taking their shot at the highest possible level, readjusting via community college, and then trying again? In retrospect, it might, but only the player and their families can decide this, and only in retrospect.
You ask about the coaches role? Recognize that it would probably be a difficult task for any coach to say to a player who is batting 5-9 in his very strong lineup, especially during a championship season, 'well, we have a great team here, and, that big hit you got is only because you are getting great pitches to hit because every time you come up, guys are on base and the top of the order is right behind you -- so, just because school X is here to watch our game, pay no attention to their offer if it comes.'
When some of these kids get to college at any level, they are competing with kids who batted 1-4 and were the ones pitched around because their 5-9 in high school did not even think about playing college baseball. Same applies to successful high school pitchers who had great defenses and offenses behind them. My point is you never really know about how strong a player is unless you see them a lot, in all different types of situations, and even then, projecting the additional physical development that will occur from age 17-18 to 20+ is very, very difficult.
So, should the coach help sell his players to schools, yes. He needs to represent their current ability and projectabilty as best and honestly as he can. I think all coaches do this, otherwise they would lose their credibility instantly. Should he advise the players and parents as to how competitive the college process is, yes. He certainly has college experience and can speak to how well prior players or peer players have succeeded or failed at various collegiate levels, both from baseball and academic perspective. Should the coach make a recommendation about what level (high D-1 vs mid D-1 vs low D-1 vs high D-2 vs mid D-2 vs high D-3 etc) and what school within those levels his players should be considering? Yes, I believe he should provide inputs to his players, but recognize that ultimately, it's not his decision.