Our kids do them too - science and heritage. My DD10 has three boards now and DS8 just finished one. It depends which class they're in as to whether or not they participate - for example, this year was DD10's 2nd science and 1st heritage, while DS8 hasn't done a science yet but has now done a heritage.
Epoh your DS's board looks great

It's very similar to the boards I've seen in my kids' classes. Some are not as good of course, and some are fabulous to the point where you wonder how much parent help they had, and then there are the genuinely capable kids (like yours:) ) who just pull it off mostly or all themselves and shine.
I wouldn't worry about what the school thinks. A friend of mine is a teacher and she's spoken to other teachers who really hate grading them because you don't know how much of the grade belongs to the student or the parent, lol.
What really matters is how much the student learns from the project - not just about the subject matter, but about the process of taking a topic, learning about it, organizing the information and then presenting to others. It sounds like your son accomplished this objective in spades (and his board looks genuine and fabulous

)