According to Crager it just means that instead of unilug or multi pattern lug spacing it means a wheel that fits a single pattern like 5/4.5". It just another sales tactic.
Until a while ago, you could get a Cragar S/S only as a unilug wheel. That wheels are sometimes hard to center and can cause some vibrations at higher speeds. That problem is solved with their new version of the "direct drill" S/S which uses only one specific bolt pattern (like 5x4.5).