That's not how a lawnmower works. The first blade of grass taller than the lawnmower blade height encountered is cut first.

I suppose what it could mean is the field with the tallest grass gets the lawnmower first. Then again all that matters is if the grass is taller than the blade, not how much taller.

Indeed, why would you avoid shortest straw, if the tallest grass gets chopped first?

I think he meant "The tallest blade of grass is the first to be mowed down", but that's not during "turbulent times", it's when you are mowing your lawn. I guess that's turbulent for the grass.