The gear box oil is the same as the engine oil. How it moves through the drive itself is more up the design engineers.
I have never seen an open gear box. They are not normally changed by itself. If one fails (rarely), the complete engine is changed.
Spay nozzles are designed to apply oil directly on to a bearing or component. The oil must "flow" for cooling purposes. Parts are not submerged in oil. They get fresh cool(er) oil which is pulled down by gravity to a sump, then to a pump..... fuel/oil, air/oil cooler, or both.....and then it starts the journey all over again.