There are always instances where something can't be used and the end results are still exactly the same. On a Victor intake, you can't use the rocker tins, but somehow everything still magically works. On roller lifter engines, valley tins can't be used, but still everything somehow works just as well. Ford quit using oil slingers in the late 70's and if we leave them out today, everything somehow works just as good.
If you have them and are compelled to use them, that's fine. But if you leave them out, everything will still work just as good. I promise.
To this day, I haven't used one single valley tin, rocker tin, or oil slinger in any engine I've built. You won't find any of the old factory tins in my shop anywhere.