Okay, so I've found something interesting, but first let me start off by explaining this:
Left is FC, middle is NES, right is my translation
The original line with the words rendered in kanji is：「土 日 水 風 の ４つのクリスタルはそれぞれの力によって輝いている。４匹のカオスがそれを遮って力を手に入れようとしている。」
A literal-style awkward translation would be: Earth Fire Water Wind, each of those four crystals shine with a power. The four Chaos interrupted those powers and have "put it in their hands"(typical expression for obtaining something)
And I'm writing that line as, "Earth, Fire, Water, Wind. The four Crystals each shone with a special power. The Four Fiends of Chaos have seized those powers for their own use."
Out of curiosity, I wanted to see what the GBA translation did, so I checked, and this is what I found that's interesting:
(credit to Youtuber Cendril89 for these pics of which I took screenshots of)Yup, looks like "Four Fiends of Chaos" is canon.
And this is what the Japanese GBA version says, which is different from the original FC text even when applying kanji to the FC text (Compare with the FC version screenshot up above):
(credit to Youtuber くるとん for these pics of which I took screenshots of)
"The four Crystals that exist in this world..." "Have now lost their light. The four Chaos have interrupted those powers and have "put it in their hands"(typical expression for obtaining something)
It's already at the top of this post but here's the original FC line so you don't have to scroll up: 「土 日 水 風 の ４つのクリスタルはそれぞれの力によって輝いている。４匹のカオスがそれを遮って力を手に入れようとしている。」
So, main point is, looks like the English GBA version refers to them as "Four Fiends" but has that one sage say "Four Fiends of Chaos" as a full title, which is what I thought would be the best way to go anyways!