I would say yes, observe them. What you are learning by doing this is "string dampening" (muting strings). This is a vital Right Hand technique.
For example, when playing the music of Bach and observing the rests in the bass melody, you are helping to define and give extra texture to the bass melody (as opposed to just letting every bass note ring out). In some instances when playing music (such as Sor Study No. 4 in D major : study of playing melody in the bass / thumb control), you will be playing melodic lines across numerous bass strings, and will need to dampen already vibrating strings in order to not obscure or blur the melody (I hope that makes sense).
Overall, yes observe them. String dampening is a necessary technique to have in your arsenal.
"Not all those who wander are lost." - J.R.R. Tolkien