Yes that’s true as a general rule. Usually Mon and Sat are the busiest *MK days within any given week.
On the flipside, Wed and Thurs are usually the best MK days within any given week, and Tues sometimes.
Epcot usually is busier on the weekends, especially food booths. WDW puts the EP extra evening hours on Monday, likely because least busy day of the week. (They are also trying to fill hotel booking gaps)
HS seems more consistent in crowds, typically doesn’t have large swings day to day.
AK is more of a crap shoot though we try to avoid Sundays. Thurs can be good.
We use this to start building our park days plan. We follow where possible but not sticklers.
*MK during party season (
MNSSHP and
MVMCP) is a different story lol. Then non-party days are OFF THE CHARTS!