It can assist you in kuzushi if you are not in control of the core and allow you to move in a manner to control the core more effectively...but it is not the lock itself that matters to me as it is only a means to an end.
This is assumes that your endstate is to submit or sustain control of an individual for a period of time
That sounds about right. When we use Sanke jo, it's preparatory to a throw or pin. In the case of escaping a headlock, it'd be to break the lock so you could pivot away and transition into another technique.