Rake is the difference between the axis of steering and the center line of the axle in the wheel.

If you are putting a 650C sized fork in a 700C sized frame you are also changing the head angle, increasing it,

by using a shorter fork and a smaller diameter wheel 571 . rather than 622 .

so you are changing the trail , that is the measurement on the ground ,
where the line thru the head angle crosses the vertical line thru the axle.

more rake/offset reduces the trail if the head angle axis stays the same

change the head angle too, and you throw in another variable ..