I have flown my Mk III from grass, gravel, concrete, bitumen and etc etc for over twenty years.
Grass is fine.
BUT not long wet grass, nor grass with hidden wombat holes or rabbit holes.
(Here in Australia we did not have rabbits until Bill Allen's countrymen brought them in for food!!! Sorry, how are you Bill?)
Soft sand is a no-no.
SHORT wet grass (morning dew) is OK but NOT anything your little tyres can sink into or get caught up in.
A hard surface with short grass and no holes is not a problem.
The outback is called that for a reason. It has another name, the GAFA - the Great Australian F All.
There are places where sealed runways are a luxury reserved pretty much for airline and such services that can pay for them.
Have a look at the wheel spats in the Old Station photo - those tyres are not in long grass or sinking into the surface.
Google Earth at 23 deg 49.45'S, 150 Deg 48.92'E and you can see the grass strip and grass taxiway; good spot for a fly-in even in a Cozy
Warrenvale is a cattle station with a gravel "all weather" strip. You'll find it here: https://www.stanbroke.com/the-stanbroke-story/
and on Google Earth at 18 Deg 25.116'S 140 Deg 47.289'E (Look really close up!!)
It is gravel except after the monsoon when it gets a bit of grass - don't use it wet!!
Whilst on Google Earth have a look at some of the so called "airports" in the area and you will not see too many you would give that gradiose description to!
The Royal Flying Doctor service operates into many of these places with King-Airs and many are suitable for Cozy / Long Eze types IF you check the length and the surface first.
Grass is fine - SHORT, NOT LONG or SOAKING WET, FIRM SURFACE below.
Gravel is usable but use the speedbrake on initial take off roll to keep stones out of the prop.