Here is the pic of the used Neil Miller strop I bought secondhand last week, obviously some metal coming off onto the flax linen and it feels like it is doing something unlike the cheap one I had previously
I'm using mostly Kanoyama strops after honing on jnats. I use the Kanoyama canvas, 20 strokes, then 35 suede and 65 cordovan. The canvas seems to smooth the edge a bit, but I did not find that flax linen helped or smoothed a good jnat edge. Flax linen does seem to help a coticule edge.
i think that you just have to try different fabric components and see if they help, hurt, or do nothing for the different types of finishers that you use.