Lol. Good one
It never said which order they had to be in. They say reading is fundamental.
That makes the riddle untrue, there are more than three words that end in the letters gry, actually I believe I read up on this riddle on snopes and there are actually more than three words that end in gry. Gry itself is a word:
From Webster's revised unabridged Dictionary:
Gry
Gry\, n. [Gr ? syllable, bit.]
1. A measure equal to one tenth of a line. [Obs.] --Locke.
2. Anything very small, or of little value. [R.]
When people reworded/shortened the riddle, they messed it up.