That's definitely the case. Nintendo even instituted a 5 games/year limit on publishers to limit the chances that they'd flood the market. Nintendo would have a group internally playtest games and provide feedback to publishers. Because the NES was so popular and games were cheap to develop, some publishers would submit more than 5 games per year and only publish the games that scored highest. As a result, there's tons of fully complete NES games that never got released.