I really question this.
As a rule, as a generality, as a norm, as far as crowd patterns go this is the mother of all misconceptions on these boards.
When one park is packed they all are --more or less. The overall crowd patterns in the parks(outside of special events or grand openings and the like) distribute among the parks relatively equally. High season and holiday crowds apply to all parks. Value season crowds apply to all parks. You ordinarily don't go from wall to wall guests at Animal Kingdom, hop on a transport and see walk on attractions in EPCOT.