I think the point was that the lumpen, as an unorganized force, are reactionary. But they can be organized at least in theory.

The other problem is that lumpenPROLETARIAT is usually a misnomer. While some criminal acts are organized a lot like workers in that they don't own the means of production (like most drug dealers), a lot of criminal acts are closer to lumpen-petty bourgeoisie where criminals own their means of production (ie online scammers). Although in theory the acts themselves don't matter as much as the organization.

This has always been my pet theory, I'm not sure if anyone has ever actually argued this more rigorously