The new /enrol/category/* plugin replaces old category level role assignments with original course:view (student, teacher and editingteacher roles mostly).
It is not recommended for new sites, instead people could use cohort sync plugin.

In order to enable this plugin on new sites admin has to allow enrol/category:synchronised and allow category level assignments, upgrades configures this automatically when category level enrolments detected.

Internally the sync is implemented via role (un)assignment event listeners and full sync cron job.