From Quake Wiki

This extension merely indicates that MOVETYPE_PUSH supports avelocity, allowing rotating brush models to be created, they rotate around their origin (needs rotation supporting qbsp/light utilities because id ones expected bmodel entity origins to be '0 0 0', recommend setting "origin" key in the entity fields in the map before compiling, there may be other methods depending on your qbsp, most are more complicated however).

Tip: level designers can create a func_wall with an origin, and avelocity (for example "avelocity" "0 90 0"), and "nextthink" "99999999" to make a rotating bmodel without any qc modifications, such entities will be solid in stock quake but will not rotate)