Im confused what relevance does a historic solid wall to my question. In the UK Helifix only seem to stitch cracks in the outer non bearing leaf when there has been movement. I think it may be laziness as removing plaster and various fixtures / fittings is too much hassle.
I have never seen that in the UK please expand on a cavity wall with load bearing twin wythe detailing. I really am all ears although I am not sure it answers the original question.
I dont understand why these companies dont tend to install crack stitching on the inner leaf of masonry cavity wall properties just the outside skin. After all the inner skin carries the load ?
