I would think the dipper tray acts as a windage tray in an engine with pressurized rod bearings.
https://www.enginelabs.com/engine-te...o-we-fight-it/
The idea behind a windage tray is that they provide a physical barrier between the violently moving crank with the oil it's throwing everywhere, and the oil supply, while still allowing oil to move back into the oil supply in a smoother, calmer manner.