Having a shake before and during training can be a better approach. This explains why. But a post-workout shake doesn't really have anything to do with "building definition in muscles" - that comes from basic fat loss.
Around training, fast protein and carbs yield better in-gym performance and recovery than just one or the other. So they're right as far as that.
Most coaches recommend prioritizing carb intake around training even when following a low carb diet, because that's the one time of day when your body has the biggest demand for carbs. As long as you're training volume and intensity is sufficient, there's basically no problem having even the majority of your day's carbs right before, during, and right after training.
In this thread, Christian Thibaudeau discussed the workout nutrition he uses with the CrossFitters he coaches. Spoiler: It's Plazma, Surge Workout Fuel, and Mag-10, depending on what type of workouts they're doing (strength vs metcon).
Based on a quick Google, the two products you mentioned would end up costing more than SWF while delivering different nutrition (whey and glucose compared to leucine and cyclic dextrins, plus other performance-boosting nutrients I didn't see in the 1stPhorm stuff like a hydration complex, citrulline, and beta alanine).