If you think about the Slinger, well...
I have heard people say when tearing into a 273 or poly they didnt have one, now then there are those who forget them or choose not to use them.... then there is that bolt up top that drips oil...and that drip plate...some having it while others didn't as well.. You dont need this and that, but they can help... because think about it every time you slow down, brake...some oil rushes up to the crank gear from what's flung off the crank and running back through the valley drain backs, ...and general 'windage'. The slinger more so holds the oil that hits it and kinda captures it like a barrier/catcher, holding more oil for the front gear and chain to carry up 'to draw like a convayer belt' up to the cam gear. The chain is moving the oil mostly.
I run a bolt/w hole on the cam plate and a slinger in the 410, no director plate. My 340 uses a tensioner, it has the drip/oil director built in and a slinger down low.
No diff.
It doesnt hurt...but consider they were trying to stretch the life of a 'silent chain' with all those oiling tricks and NOT a sturdy roller chain like we replace them with.