Are these integrated diagonal wall braces structurally important?
Sometimes framing of a short internal wall that TEE's into an exterior wall is braced that way if the exterior wall is:


The exterior wall extends a long distance on either side of the TEE
And the exterior wall is parallel to ceiling joists and floor joists
And has a high gable end wall above this area. 


Intention was to eliminate a lot of flex in the exterior wall both during construction and when there is possibility of large gusty wind loads on the wall. You will see less of this with much construction moving toward 2x6 studding for exterior walls. Metal X banding nailed to the face of the studs is also a better way to achieve this result.

Repeating from Isherwood. Make sure to put double stud at the left and right side of your opening. A single 2x4 is just not stiff enough and you will really appreciate it being there when you come to install door casing or trim.