The reason why the case is universal, unlike the LC 550, is because the 630 Series came out in 1994, not 1993. Apple began using a lot of standardized case parts to save money that year (a hallmark of Mike Spindler-era Macs).

You can even see this to a degree on the LC 500 series. The LC 520 has a plastic piece for its nameplate. The later 500 series had stickers.

IMO, 1993 was the last good year for Mac design (until 1998).