Glove side isn't really a "spot." More of an area. It's the entire section of the net above the goaltender's leg pad, and under the bar, on the glove side. A goaltender can't simply cheat to cover that entire side on the shootout. Not without opening up a massive hole on the blocker side. What you're suggesting isn't really feasible.
A goalie can anticipate the shot to that side, but that's it. There is too much net to cover, and the release that Silfverberg has allows him to beat the goaltender cleanly, and consistently. We've seen it enough times to see that if Silfverberg hits the spot he wants, it's going in.