It could mean that Ventura considers spring exhibition games meaningless, meaningless enough to put two third basemen in the game at the same time. It could be a recognition that stuff happens during a long baseball season. There was a game in 1994 when Ventura had to move over to short in an emergency, without great success. It's possible that Ventura appreciates the value of playing players out of position in meaningless games.
Morel played a few games at shortstop for Charlotte in 2010, but I don't believe playing short in a spring training game means he is being groomed as a backup shortstop. I would be very surprised and rather disappointed if Sanchez doesn't make the team in favor of Morel backing up short.