Considering I know a few people who took the Upswing course, i can only say that it only taught them about math part of the poker. If a player was to follow those charts in the very long run, should be on the + side of the game.
BUT, it doesn't tell anyone how to maximize on those charts, what hands to mix in, how to behave in unfamiliar situations. If you look at hands Doug played (you can find tons on YT), it is obvious he doesn't follow his own charts completely. He mixes in hands, positions, I will guess mostly based on opponents and reads.
So, don't take online courses for granted, they are not some huge money bringers on their own, it is just tons of advices that should help you in your game..