Is this allowed?

My S is a rising sophomore and received an email from the head coach of the University of Chicago inviting him to attend one of their five home games this upcoming season. The email states that “NCAA rules allow us to provide prospects with up to three complimentary tickets to a game. If you would like to attend a game please let Coach XXXX XXXX know via email the date and number of tickets. He will make sure to add you to our pass list for the game.”
This won’t affect his HS eligibility? Is this really allowed?

Yes it is really allowed. If that is all that is provided (no transportation, lodging) it is an unofficial visit. Most D3 schools do unofficial visits.

Game visits in D3 are permitted.

Game visits are allowed in all NCAA divisions. Generally a school can provide up to 3 tickets gratis and some basic snacks/refreshments.