I think you are just the sort of scientist the grandparent was referring to- the sort to conflate hows and whys.
For you see, you did not answer the why correctly! The REAL answer for why the grass is green is because cows evolved to digest grass more quickly than the other grass eaters, and the more green the grass, the faster the cows could eat it. And the faster the cows ate the greener grass, the faster the green grass growed all around (seed dispersal). So you see, the reason WHY the grass is green is because cows evolved to digest grass better than horses did bluegrass. (The cows digested the green grass at 2x the rate that horses digested the bluegrass.)
No wait- That's not right. The realER reason why is that shorthaired dragons ate all the pelaquapods (the ancient cow's first hay eating competitor)- leaving the cows to splurge on all the world's hay- which they did. Until many millennia later, when ironically the longhaired shorttailed dragons arrived on the scene stealing every last bit of hay from the cows- forcing them to begin adapting by dabbling in grass. (Many died off due to starvation initially.) But eventually, adapt they did. And the rest, as you know, is history.
Wait, wait... one more try. Because the last remaining member of a certain species of giant squid ate a catfish that ate a carp dropping that contained the residual poison from sunk dead rats, having been poisoned by some cruel sorts aboard the Nina, Pinta, and Santa Maria and then themselves eaten by Arctic Carp. The last of the giant squid's demise cleared the way for the Turquoise Tortoise to move into the area and multiply- no longer fearful of being giant squid supper. Multiply they did, and for good reason. WHY you ask? So that their descendants could go forth and multiply- which they did- until finally the most special day arrived- the day their seed would give rise to a new inhabitant of the blue planet.... the first cow.
Oops- wrong again. The most REALEST reason why is this! A while back, a supernova exploded, and there were remnants. These remnants were dust, and they were us. We were stardust. THAT is why!
Actually I think you were really talking about hows, not whys. It seems that you latched on to an amalgamation of hows, creating in your own mind the illusory emergent property of the why- after which you took this imaginary why, compatible with your ends as it was, and used it to make yourself feel and appear scientific. And that's the how of it.