Removing the cartilage allows you to open the pockets all the way out to the edges which gives generally gives you more detail and reduces any edge curl when drying. Plus, without cartilage the pocket can more easily accommodate your liner, facilitating its insertion...your not fighting with a more rigid/reduced space. Moving the adhesives around to distribute evenly can be controlled more effectively without cartilage. Bondo can be used effectively by talented folks but many ears I have seen done that way just don’t seem to measure up to what can be achieved with liners. Personally, I like the prolonged workability with liners as I’m always tweaking things for the first several hours anyway. Whereas, Bondo requires you have it right before you mount it up.