The recording technique described in the video is actually something very important that you must understand about mastering. Middle C on a grand piano in a studio with great acoustics and multiple full range mics will cover a much broader range on your Eq than a toy casio keyboard recorded with your phone. In fact, the toy casio will look much like the little "hump" that the guy draws in the video. Yes, this is an extreme comparison, but you can learn from it. With enough manipulation, you can Eq the grand piano to sound more like the casio so it will stand out and fill a specific range in your mix.

The fact that BIAB takes all the "thinking" out of the process and does all that for you is not necessarily a "bad" thing. You just have to accept that you're being limited by the presets built into the program. However, for a well trained ear those presets can be very annoying. Too much "technique" will squash the overall dynamic of your recording.