well... there is sorta a difference in that 'knitting' is a broad, all encompassing title for the yarn manipulation we do, garter stitch just happens to be one (of many) ways to knit. If you were wanting to do garter stitch in the round, you would also have to purl, so garter doesn't really
mean knitting, it just involves the knit stitch.
but yeah, that instruction is weird
What are you making?