Interesting that thing you/they say about “natural visualisation”. I remember from back in the days I was flying gliders that the most prolific such visualisation were those big fluffy white things… Maybe sometimes the odd hawk or kite - but you mostly only spot them when you’re in the thermal with them already. And certainly never grass (they should give us better control over the grass growing on the ground before they want to make it fly 
)
On a related note: Someone just resurrected my historic thread where some of this was already discussed in depth. So for completeness’ sake: