It seems to be accurate for the most part. The article itself reads, however, that the original Seiken Densetsu was intended to a side story to FF, and that it was similar to FFIII, the most recent FF installation at the time. FFIII, which included moogles, was originally released in 1990, and Seiken Densetsu in 1991. Thus, I'm not sure how it is that they're claiming that moogles first appeared in Seiken Densetsu. I suppose it could be because FFIII wasn't released outside Japan at the time, but that wouldn't reflect the actual first appearance.

It's also worth noting that there were beavers in FFII that Guy/Gus could communicate with. These beavers bore a striking resemblence to moogles and can probably be considered their predecessors.

The picture on the side is that of a moogle from FFTA.