The presence or lack of contrast is not a good nor bad thing. Rather, when you are aware of it and have a sense of your personal tastes, you can use these principles to really nail down your tone and style.
Personally, I love constant vibrato and would prefer the lack of it to be more noticeable than the presence of it.
Another example – The modern tsugaru aesthetic encourages playing in ushirobachi position (closer to the bridge) for a booming tone.
In the modern tsugaru style, ushirobachi position is the center of the dou, which yields the loudest strikes
Well, when not playing in tsugaru style, I prefer the booming tone to have greater contrast, so I will play in ushirobachi position sparingly to make that powerful tone more pronounced.
