FWIW: before cold starting a Rotax 4-stroker, I was taught to check the oil level by opening the reservoir, then rotating the prop by hand until hearing from the reservoir a noise like flushing the loo, then apply the dipstick. But other pupils started the engine for a minute, then stopped it to check. Not sure which is best, likely it is the most troublesome...
When hand-turning the prop, it has to be done counterclockwise (as one looks at it) otherwise air might be sucked into the oil circuit. That's to say, if my dusty memory is to be trusted.
This is true but has nothing to do with the original thread.
On the Rotax 4-stroke (912/914) there's a separate oil reservoir but there's no pump between the sump and this reservoir. Instead, blow-by from the cylinder gases past the piston rings provide pressure in the crankcase to push the oil into the reservoir.
To ensure that all oil has returned to the reservoir, so that you can take an accurate measurement of the oil level in there, you hand-turn the prop slowly (with the ignition off, obviously). The hissing sound is the piston blow-by, and the burbling sound means that all oil has been pushed back. What you're hearing is the crankcase air burbling in the oil reservoir.
Starting the engine for a few seconds would work too, but only if you are absolutely sure that there's oil in the engine/reservoir to begin with. And that was the purpose of the pre-flight wasn't it?