When I've put motors together that's what I've done.....follow the manufacturer's recomendations, it generally works out best that way.
But the question remains unanswered....
Is this (built in) advance to compensate for timing chain stretch?
Let's say you were going to build two idendical motors....with one minor difference. One uses a timing chain and the other uses a gear drive.
Would you install the cam the same way? Or would it be different?