over the years, I have traded "anything under the sun", also a few things that are not under the sun :)
And yet, over the last 20-years 100% of my 401-K is invested in S&P500. It is not VOO exactly, it was VFNIX first, then they moved to fidelity and now I have their equivalent. Just like banks they change your 401-K custodians too. Good simple plan that your son started on, if he sticks to it, that is a easy way to be financially free.
I refuse to pay someone to make me less money than I do.