If his flight to EWR is delayed, he could be screwed with a capital F. Not worth risking it.
Because it's a separate reservation, airlines will often absolve themselves of the duty to re-book in case of a missed connection. If he doesn't show up at the VS gate on time, he could have big problems getting to his destination. CO may or may not be willing to work with him, and since the travel is via partners on award tickets, you're at the mercy of award availability on partners for re-booking. If there are no award seats available, he'll be stuck.